Organic electroluminescent element, lighting device, and display device

ABSTRACT

This organic EL element has two blue light emitting units, and has, in the emission spectrum thereof, one or two peak wavelengths in a blue light wavelength range of 440 nm-490 nm. In this organic EL element, the correlated color temperature of white light is 3300K or greater, R6 is 60 or greater, and R12 is 30 or greater.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent elementand to a display device and a lighting device including the same.

The present application claims the benefit of priority of JapanesePatent Application No. 2016-254302 filed on Dec. 27, 2016, the contentsof which are incorporated herein by reference.

BACKGROUND ART

An organic electroluminescent element (hereafter, also referred to as“organic EL element” for short) is a self-luminescent element includinga light emitting layer, made of an organic compound, between a cathodeand an anode facing each other. When voltage is applied between thecathode and the anode, electrons injected into the light emitting layerfrom the cathode side and holes injected into the light emitting layerfrom the anode side recombine in the light emitting layer to formexcitons and the excitons causes the organic EL element to emit light.

As an organic EL element capable of achieving high luminance and longlifetime, there is known an element with a multi-photon emissionstructure (hereafter, referred to as “MPE element” for short) in which alight emitting unit including at least one light emitting layer isconsidered as one unit and an electrically-insulating charge generatinglayer is arranged between multiple light emitting units (for example,see Patent Document 1). In the MPE element, when voltage is appliedbetween a cathode and an anode, charges in a charge transfer complexmove to the cathode side and the anode side. In the MPE element, holesare thereby injected into one light emitting unit located on the cathodeside of the charge generating layer and electrons are injected intoanother light emitting unit located on the anode side of the chargegenerating layer. In such an MPE element, since light can besimultaneously emitted from the multiple light emitting units with thesame current amount, a current efficiency and an external quantumefficiency multiplied by the number of the light emitting units can beachieved.

Moreover, the MPE element can provide white light by combining variouslight emitting units configured to emit light of different colors.Accordingly, in recent years, there are developed MPE elements aimed tobe applied to a display device and a lighting device which basicallyemit white light. For example, there is known an MPE element suitablefor a display device which generates white light with high colortemperature at high efficiency by using a combination of a lightemitting unit configured to emit blue light and a light emitting unitconfigured to emit green light and yellow light (for example, see PatentDocument 2). Moreover, there is known an MPE element suitable for alighting device which generates white light with high color temperatureand an excellent color rendering property by using a combination of alight emitting unit configured to emit red light and a light emittingunit configured to emit blue light and yellow light (for example, seePatent Document 3).

Although the display device and the lighting device both use whitelight, required performance specifications vary between these devicesand MPE elements with structures dedicated to the respective deviceshave been developed. For example, as described in Patent Documents 2 and3, in the development of MPE elements characterized by emission of whitelight with high color temperature, luminous efficiency is focused on inthe development of the MPE element for the display device while a colorrendering property is focused on in the development of the MPE elementfor the lighting device.

However, from the viewpoint of obtaining excellent white light, it isideal in both of the display device and the lighting device that theelement can provide white light which is excellent not only in some ofthe characteristics but also in all three important indices of whitelight, that is color temperature, luminous efficiency, and a colorrendering property in a balanced manner.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Patent Application Publication No.2003-272860

Patent Document 2: Published Japanese Translation of PCT InternationalApplication No. 2012-503294

Patent Document 3: Japanese Patent Application Publication No.2009-224274

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The present invention has been proposed in view of the aforementionedconventional circumstances and an object thereof is to provide anorganic electroluminescent element which can provide white light withhigh color temperature, high luminous efficiency, and an excellent colorrendering property and is thus suitable for both of a display device anda lighting device and to provide a display device and a lighting deviceincluding this organic electroluminescent element.

Means for Solving the Problems

To achieve the above object, provided are the following aspects.

(1) An organic electroluminescent element having a structure in which aplurality of light emitting units each including a light emitting layermade of at least an organic compound are stacked one on top of anotherbetween a first electrode and an second electrode with a chargegenerating layer sandwiched between each pair of the adjacent lightemitting units, characterized in that

the organic electroluminescent element comprises at least two blue lightemitting units each including a light emitting layer formed of a bluelight emitting layer which emits blue light with one or two peakwavelengths in a blue wavelength band,

white light produced by light emission of the plurality of lightemitting units has an emission spectrum continuous over a wavelengthband of at least 380 nm to 780 nm and has one or two peak wavelengths ina blue wavelength band of 440 nm to 490 nm in the emission spectrum,

correlated color temperature of the white light is 3300 K or higher, and

R6 and R12 among special color rendering indices (Ri) of the white lightare 60 or more and 30 or more, respectively.

(2) The organic electroluminescent element according to the above aspect(1), characterized in that R12 among the special color rendering indices(Ri) of the white light is 60 or more.

(3) The organic electroluminescent element according to the above aspect(1) or (2), characterized in that the blue light emitting layer isformed of a blue fluorescent light emitting layer containing a bluefluorescent material.

(4) The organic electroluminescent element according to the above aspect(3), characterized in that the blue light provided by the blue lightemitting unit including the blue fluorescent light emitting layerincludes a delayed fluorescence component.

(5) The organic electroluminescent element according to the above aspect(1) or (2), characterized in that the blue light emitting layer isformed of a blue phosphorescent light emitting layer containing a bluephosphorescent material.

(6) The organic electroluminescent element according to anyone of theabove aspects (1) to (5), characterized in that

the organic electroluminescent element comprises two of the blue lightemitting units which are identical, and

the blue light emitting units emit blue light with the same peakwavelength.

(7) The organic electroluminescent element according to anyone of theabove aspects (1) to (5), characterized in that

the organic electroluminescent element comprises two of the blue lightemitting units which are different from each other, and

the blue light emitting units emit blue light with different peakwavelengths, respectively.

(8) The organic electroluminescent element according to the above aspect(7), characterized in that the white light has one peak wavelength in ablue wavelength band of 440 nm to 470 nm and one peak wavelength in ablue wavelength band of 470 nm to 490 nm.

(9) The organic electroluminescent element according to anyone of theabove aspects (1) to (8), characterized in that

the organic electroluminescent element comprises at least one red/greenlight emitting unit including a light emitting layer formed by stackinga red phosphorescent light emitting layer which emits red light with onepeak wavelength in a red wavelength band and a green phosphorescentlight emitting layer which emits green light with one or two peakwavelengths in a green wavelength band one on top of the other, and

the white light produced by the light emission of the plurality of unitshas one peak wavelength in a red wavelength band of 590 nm to 640 nm andone or two peak wavelengths in a green wavelength band of 500 nm to 560nm.

(10) The organic electroluminescent element according to any one of theabove aspects (1) to (8), characterized in that

the organic electroluminescent element comprises at least one red-greenlight emitting unit including a light emitting layer formed of a mixedlayer of a red phosphorescent material and a green phosphorescentmaterial, and

the white light produced by the light emission of the plurality of lightemitting units has one peak wavelength in a red wavelength band of 590nm to 640 nm and one or two peak wavelengths in a green wavelength bandof 500 nm to 560 nm.

(11) The organic electroluminescent element according to any one of theabove aspects (1) to (10), characterized in that a light emissionintensity of the peak wavelength in the blue wavelength band of 440 nmto 490 nm is higher than either of a light emission intensity of thepeak wavelength in the red wavelength band of 590 nm to 640 nm and alight emission intensity of the peak wavelength in the green wavelengthband of 500 nm to 560 nm.(12) The organic electroluminescent element according to the aboveaspect (11), characterized in that the white light has one bottomwavelength in a blue wavelength band and a green wavelength band of 500nm to 520 nm.(13) The organic electroluminescent element according to the aboveaspect (12), characterized in that a light emission intensity of the onebottom wavelength in the blue wavelength band and the green wavelengthband of 500 nm to 520 nm is lower than a light emission intensity of abottom wavelength in a wavelength band of 570 nm to 590 nm.(14) The organic electroluminescent element according to the aboveaspect (12) or (13), characterized in that a ratio of (B) to (A)((B)/(A)) is 0.50 or smaller, where (A) is a light emission intensity ofa peak wavelength having the highest light emission intensity in thewavelength band of 380 nm to 780 nm and (B) is a light emissionintensity of the one bottom wavelength in the blue wavelength band andthe green wavelength band of 500 nm to 520 nm.(15) The organic electroluminescent element according to any one of theabove aspects (1) to (14), characterized in that an average colorrendering index (Ra) of the white light is 70 or more.(16) The organic electroluminescent element according to any one of theabove aspects (9) to (15), the organic electroluminescent element havingthe structure in which the plurality of light emitting units eachincluding the light emitting layer made of at least the organic compoundare stacked one on top of another between the first electrode and thesecond electrode with the charge generating layer sandwiched betweeneach pair of the adjacent light emitting units, the organicelectroluminescent element capable of providing the white light bycausing the plurality of light emitting units to emit light,characterized in that

-   -   the organic electroluminescent element comprises:        -   a first light emitting unit formed of the red/green light            emitting unit or the red-green light emitting unit;        -   a second light emitting unit formed of the blue light            emitting unit; and        -   a third light emitting unit formed of the blue light            emitting unit,    -   the first light emitting unit and the second light emitting unit        are stacked one on top of the other with a first charge        generating layer sandwiched therebetween,    -   the second light emitting unit and the third light emitting unit        are stacked one on top of the other with a second charge        generating layer sandwiched therebetween, and    -   the organic electroluminescent element has a structure in which        the second electrode, the third light emitting unit, the second        charge generating layer, the second light emitting unit, the        first charge generating layer, the first light emitting unit,        and the first electrode are stacked one on top of another in        this order.        (17) The organic electroluminescent element according to any one        of the above aspects (9) to (15), the organic electroluminescent        element having the structure in which the plurality of light        emitting units each including the light emitting layer made of        at least the organic compound are stacked one on top of another        between the first electrode and the second electrode with the        charge generating layer sandwiched between each pair of the        adjacent light emitting units, the organic electroluminescent        element capable of providing the white light by causing the        plurality of light emitting units to emit light, characterized        in that    -   the organic electroluminescent element comprises:        -   a first light emitting unit formed of the blue light            emitting unit;        -   a second light emitting unit formed of the red/green light            emitting unit or the red-green light emitting unit; and        -   a third light emitting unit formed of the blue light            emitting unit,    -   the first light emitting unit and the second light emitting unit        are stacked one on top of the other with a first charge        generating layer sandwiched therebetween,    -   the second light emitting unit and the third light emitting unit        are stacked one on top of the other with a second charge        generating layer sandwiched therebetween, and    -   the organic electroluminescent element has a structure in which        the second electrode, the third light emitting unit, the second        charge generating layer, the second light emitting unit, the        first charge generating layer, the first light emitting unit,        and the first electrode are stacked one on top of another in        this order.        (18) The organic electroluminescent element according to any one        of the above aspects (9) to (15), the organic electroluminescent        element having the structure in which the plurality of light        emitting units each including the light emitting layer made of        at least the organic compound are stacked one on top of another        between the first electrode and the second electrode with the        charge generating layer sandwiched between each pair of the        adjacent light emitting units, the organic electroluminescent        element capable of providing the white light by causing the        plurality of light emitting units to emit light, characterized        in that

the organic electroluminescent element comprises:

-   -   a first light emitting unit formed of the red/green light        emitting unit or the red-green light emitting unit;    -   a second light emitting unit formed of the blue light emitting        unit;    -   a third light emitting unit formed of the red/green light        emitting unit or the red-green light emitting unit; and    -   a fourth light emitting unit formed of the blue light emitting        unit,

the first light emitting unit and the second light emitting unit arestacked one on top of the other with a first charge generating layersandwiched therebetween,

the second light emitting unit and the third light emitting unit arestacked one on top of the other with a second charge generating layersandwiched therebetween,

the third light emitting unit and the fourth light emitting unit arestacked one on top of the other with a third charge generating layersandwiched therebetween, and

the organic electroluminescent element has a structure in which thesecond electrode, the fourth light emitting unit, the third chargegenerating layer, the third light emitting unit, the second chargegenerating layer, the second light emitting unit, the first chargegenerating layer, the first light emitting unit, and the first electrodeare stacked one on top of another in this order.

(19) The organic electroluminescent element according to any one of theabove aspects (9) to (15), the organic electroluminescent element havingthe structure in which the plurality of light emitting units eachincluding the light emitting layer made of at least the organic compoundare stacked one on top of another between the first electrode and thesecond electrode with the charge generating layer sandwiched betweeneach pair of the adjacent light emitting units, the organicelectroluminescent element capable of providing the white light bycausing the plurality of light emitting units to emit light,characterized in that

the organic electroluminescent element comprises:

-   -   a first light emitting unit formed of the red/green light        emitting unit or the red-green light emitting unit;    -   a second light emitting unit formed of the blue light emitting        unit;    -   a third light emitting unit formed of the red/green light        emitting unit or the red-green light emitting unit;    -   a fourth light emitting unit formed of the red/green light        emitting unit or the red-green light emitting unit;    -   a fifth light emitting unit formed of the blue light emitting        unit; and    -   a sixth light emitting unit formed of the red/green light        emitting unit or the red-green light emitting unit,

the first light emitting unit and the second light emitting unit arestacked one on top of the other with a first charge generating layersandwiched therebetween,

the second light emitting unit and the third light emitting unit arestacked one on top of the other with a second charge generating layersandwiched therebetween,

the third light emitting unit and the fourth light emitting unit arestacked one on top of the other with a third charge generating layersandwiched therebetween,

the fourth light emitting unit and the fifth light emitting unit arestacked one on top of the other with a fourth charge generating layersandwiched therebetween,

the fifth light emitting unit and the sixth light emitting unit arestacked one on top of the other with a fifth charge generating layersandwiched therebetween, and

the organic electroluminescent element has a structure in which thesecond electrode, the sixth light emitting unit, the fifth chargegenerating layer, the fifth light emitting unit, the fourth chargegenerating layer, the fourth light emitting unit, the third chargegenerating layer, the third light emitting unit, the second chargegenerating layer, the second light emitting unit, the first chargegenerating layer, the first light emitting unit, and the first electrodeare stacked one on top of another in this order.

(20) The organic electroluminescent element according to any one of theabove aspects (1) to (19), characterized in that

the charge generating layers are formed of electrically insulatinglayers made of an electron accepting material and an electron donatingmaterial, and

a specific resistance of the electrically insulating layers is1.0×10²Ω·cm or more.

(21) The organic electroluminescent element according to the aboveaspect (20), characterized in that the specific resistance of theelectrically insulating layers is 1.0×10⁵Ω·cm or more.

(22) The organic electroluminescent element according to any one of theabove aspects (1) to (19), characterized in that

each of the charge generating layers is formed of a mixed layer ofdifferent materials and one component of the mixed layer forms a chargetransfer complex by redox, and

when voltage is applied between the first electrode and the secondelectrode, charges in the charge transfer complex move to the firstelectrode side and the second electrode side to cause holes to beinjected into one light emitting unit located on the first electrodeside of the charge generating layer and cause electrons to be injectedinto another light emitting unit located on the second electrode side ofthe charge generating layer.

(23) The organic electroluminescent element according to any one of theabove aspects (1) to (19), characterized in that

each of the charge generating layers is formed of a laminate of anelectron accepting material and an electron donating material, and

when voltage is applied between the first electrode and the secondelectrode, in an interface between the electron accepting material andthe electron donating material, charges generated by reaction involvingelectron transfer between the electron accepting material and theelectron donating material move to the first electrode side and thesecond electrode side to cause holes to be injected into one lightemitting unit located on the first electrode side of the chargegenerating layer and cause electrons to be injected into another lightemitting unit located on the second electrode side of the chargegenerating layer.

(24) The organic electroluminescent element according to any one of theabove aspects (1) to (23), characterized in that the charge generatinglayers contain a compound having a structure expressed by formula (1):

where R represents an electron withdrawing group of F, Cl, Br, I, CN, orCF₃.

(25) The organic electroluminescent element according to any one of theabove aspects (1) to (24), characterized in that

the organic electroluminescent element comprises at least three colorfilters different from one another, and

an arrangement of the at least three color filters different from oneanother changes the white light produced by the light emission of theplurality of light emitting units to light of a different color.

(26) The organic electroluminescent element according to the aboveaspect (25), characterized in that the arrangement of the at least threecolor filters different from one another is one selected from the groupconsisting of a stripe arrangement, a mosaic arrangement, a deltaarrangement, and a pentile arrangement.(27) The organic electroluminescent element according to the aboveaspect (25) or (26), characterized in that

the at least three color filters different from one another are a redcolor filter, a green color filter, and a blue color filter, and

the organic electroluminescent element has a RGB arrangement in whichthe three color filters different from one another are arranged in turn.

(28) The organic electroluminescent element according to the aboveaspect (27), characterized in that

the organic electroluminescent element has a RGBW arrangement includingthe RGB arrangement, and

the color filters are not arranged in an arrangement portion of W.

(29) The organic electroluminescent element according to the aboveaspect (28), characterized in that the RGBW arrangement is one selectedfrom the group consisting of a stripe arrangement, a mosaic arrangement,a delta arrangement, and a pentile arrangement.(30) A display device characterized in that the display device comprisesthe organic electroluminescent element according to any one of the aboveaspects (25) to (29).(31) The display device according to the above aspect (30),characterized in that

the display device comprises a base substrate and a sealing substratewhich are formed of flexible substrates, and

the display device is flexible.

(32) Alighting device characterized in that the lighting devicecomprises the organic electroluminescent element according to any one ofthe above aspects (1) to (24).

(33) The lighting device according to the above aspect (32),characterized in that the lighting device comprises an optical film on alight extraction surface side of the organic electroluminescent element.

(34) The lighting device according to the above aspect (32) or (33),characterized in that an average color rendering index (Ra) of the whitelight is 80 or more.

(35) The lighting device according to the above aspect (34),characterized in that

the lighting device comprises a base substrate and a sealing substratewhich are formed of flexible substrates, and

the lighting device is flexible.

Effect of the Invention

According to one aspect described above, it is possible to provide anorganic electroluminescent element which can provide white light withhigh color temperature, high luminous efficiency, and an excellent colorrendering property and is thus suitable for both of a display device anda lighting device and to provide a display device and a lighting deviceincluding this organic electroluminescent element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a schematic configurationof a first embodiment of an organic EL element in the present invention.

FIG. 2 is a graph illustrating examples of an emission spectrum of whitelight obtained in the first embodiment of the organic EL element in thepresent invention.

FIG. 3 is a view illustrating results of simulation conducted to verifyeffects on R6 and R12 in a white element.

FIG. 4 is a view illustrating results of simulation conducted to verifyeffects on R6 and R12 in the white element.

FIG. 5 is a view illustrating results of simulation conducted to verifyeffects on R6 and R12 in a white element.

FIG. 6 is a view illustrating results of simulation conducted to verifyeffects on R6 and R12 in the white element.

FIG. 7 is a cross-sectional view illustrating a schematic configurationof a second embodiment of the organic EL element in the presentinvention.

FIG. 8 is a cross-sectional view illustrating a schematic configurationof a third embodiment of the organic EL element in the presentinvention.

FIG. 9 is a cross-sectional view illustrating a schematic configurationof a fourth embodiment of the organic EL element in the presentinvention.

FIG. 10 is a cross-sectional view illustrating a schematic configurationof a fifth embodiment of the organic EL element in the presentinvention.

FIG. 11 is a cross-sectional view illustrating a schematic configurationof a sixth embodiment of the organic EL element in the presentinvention.

FIG. 12 is a cross-sectional view illustrating a schematic configurationof an embodiment of a lighting device in the present invention.

FIG. 13 is a cross-sectional view illustrating a schematic configurationof one embodiment of a display device in the present invention.

FIG. 14 is a cross-sectional view illustrating an element structure ofan organic EL element in Example 1.

FIG. 15 is a view illustrating evaluation results of the organic ELelement in Example 1.

FIG. 16 is a cross-sectional view illustrating an element structure ofan organic EL element in Example 2.

FIG. 17 is a view illustrating evaluation results of the organic ELelement in Example 2.

MODE FOR CARRYING OUT THE INVENTION

Detailed description is given of embodiments of an organicelectroluminescent element of the present invention and a display deviceand a lighting device including the same with reference to the drawings.

Note that, for the sake of convenience, in the drawings used in thefollowing description, characteristic parts are sometimes illustrated inan enlarged manner to facilitate understanding of characteristics, andproportions of dimensions of constitutional elements and the like arenot always the same as actual ones. Moreover, materials, dimensions, andthe like exemplified in the following description are merely examplesand the present invention are not necessarily limited to those and canbe carried out with the materials, dimensions, and the likeappropriately changed within a scope not changing the spirit of theinvention.

[Organic Electroluminescent Element (Organic EL Element)]

First Embodiment

FIG. 1 is a cross-sectional view illustrating a schematic configurationof a first embodiment of the organic EL element in the presentinvention.

As illustrated in FIG. 1, the organic EL element 10 of the embodimenthas a structure in which multiple light emitting units 13A, 13B, 13Ceach including a light emitting layer made of at least an organiccompound are stacked one on top of another between a first electrode 11and a second electrode 12 with each of charge generating layers (CGL)14A, 14B sandwiched between a corresponding pair of the adjacent lightemitting units. The organic EL element 10 is an organic EL elementcapable of providing white light by causing the multiple light emittingunits 13A, 13B, 13C to emit light.

The organic EL element 10 of the embodiment includes the first lightemitting unit 13A, the second light emitting unit 13B, and the thirdlight emitting unit 13C.

The first light emitting unit 13A is a red/green light emitting unit ora red-green light emitting unit. The red/green light emitting unitincludes a light emitting layer formed of a red phosphorescent lightemitting layer which emits red light with one peak wavelength in a redwavelength band and a green phosphorescent light emitting layer whichemits green light with one or two peak wavelengths in a green wavelengthband. Specifically, the red/green light emitting unit is a layer formedby stacking the red phosphorescent light emitting layer and the greenphosphorescent light emitting layer one on top of the other. Thered-green light emitting unit includes alight emitting layer formed of amixed layer of a red phosphorescent material and a green phosphorescentmaterial. Specifically, the red-green light emitting unit is one layer(single layer) containing the red phosphorescent material and the greenphosphorescent material.

The second light emitting unit 13B is a blue light emitting unit. Theblue light emitting unit includes a light emitting layer formed of ablue light emitting layer which emits blue light with one or two peakwavelengths in a blue wavelength band. The blue light emitting layer maybe a blue fluorescent light emitting layer containing a blue fluorescentmaterial or a blue phosphorescent light emitting layer containing a bluephosphorescent material. The blue light provided by the blue lightemitting unit including the blue fluorescent light emitting layer mayinclude a delayed fluorescence component.

The third light emitting unit 13C is a blue light emitting unit. Theblue light emitting unit includes a light emitting layer formed of ablue light emitting layer which emits blue light with one or two peakwavelengths in the blue wavelength band. The blue light emitting layermay be either a blue fluorescent light emitting layer containing a bluefluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light provided bythe blue light emitting unit including the blue fluorescent lightemitting layer may include a delayed fluorescence component.

The first light emitting unit 13A and the second light emitting unit 13Bare stacked one on top of the other with the first charge generatinglayer 14A sandwiched therebetween.

The second light emitting unit 13B and the third light emitting unit 13Care stacked one on top of the other with the second charge generatinglayer 14B sandwiched therebetween.

The organic EL element 10 of the embodiment has a structure in which thesecond electrode 12, the third light emitting unit 13C, the secondcharge generating layer 14B, the second light emitting unit 13B, thefirst charge generating layer 14A, the first light emitting unit 13A,and the first electrode 11 are stacked one on top of another in thisorder. Specifically, the organic EL element 10 of the embodiment has anMPE structure in which the first light emitting unit 13A, the secondlight emitting unit 13B, and the third light emitting unit 13C arestacked one on top of another with each of the first charge generatinglayer 14A and the second charge generating layer 14B sandwiched betweenthe corresponding pair of adjacent light emitting units.

In the organic EL element 10 of the embodiment, the white light producedby light emission of the first light emitting unit 13A, the second lightemitting unit 13B, and the third light emitting unit 13C has an emissionspectrum continuous over a wavelength band of at least 380 nm to 780 nm.Moreover, in the organic EL element 10 of the embodiment, the whitelight has one or two peak wavelengths in the blue wavelength band of 440nm to 490 nm in this emission spectrum. Furthermore, in the organic ELelement 10 of the embodiment, the white light has one peak wavelength inthe red wavelength band of 590 nm to 640 nm and one or two peakwavelengths in the green wavelength band of 500 nm to 560 nm in thisemission spectrum.

Generally, a metal with a small work function, an alloy of such a metal,a metal oxide, or the like is preferably used as the first electrode 11.For example, as a metal forming the first electrode 11, it is possibleto use a metal single substance like an alkaline metal such as lithium(Li), an alkaline earth metal such as magnesium (Mg) or calcium (Ca), ora rare-earth metal such as europium (Eu) or use an alloy containing anyof these metals and aluminum (Al), silver (Ag), indium (In), or thelike.

Alternatively, the first electrode 11 may have a configuration in whichan organic layer doped with a metal is used in an interface between thefirst electrode 11 and an organic layer as described in, for example,“Japanese Patent Application Publication No. Hei 10-270171” and“Japanese Patent Application Publication No. 2001-102175.” In this case,it is only necessary to use an electrically conductive material as thematerial of the first electrode 11 and the material is not limited toone with particular properties such as the work function.

As another alternative, the first electrode 11 may have a configurationin which an organic layer in contact with the first electrode 11 is madeof an organic metal complex compound containing at least one typeselected from the group consisting of alkali metal ions, alkaline earthmetal ions, and rare-earth metal ions as described in, for example,“Japanese Patent Application Publication No. Hei 11-233262” and“Japanese Patent Application Publication No. 2000-182774.” In this case,a metal capable of reducing the metal ions contained in the organicmetal complex compound to metal in vacuum, for example, a metal (with athermal reduction property) such as aluminum (Al), zirconium (Zr),titanium (Ti), and silicon (Si) or an alloy containing any of thesemetals can be used as the first electrode 11. Among these, Al which isgenerally widely used as a wiring electrode is particularly preferablefrom the viewpoint of ease of vapor deposition, high light reflectance,chemical stability, and the like.

The material of the second electrode 12 is not limited to a particularmaterial. When light is to be extracted from the second electrode 12side, a transparent, electrically conductive material such as, forexample, ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) can be used.

Moreover, in contrary to a general organic EL element, light can beextracted from the first electrode 11 side by using a metal material orthe like for the second electrode 12 and using a transparent,electrically conductive material for the first electrode 11. Forexample, by employing the method described in “Japanese PatentApplication Publication No. 2002-332567,” the first electrode 11 made ofthe aforementioned transparent, electrically conductive material such asITO and IZO can be formed by sputtering which does not damage an organicfilm.

Accordingly, when both of the first electrode 11 and the secondelectrode 12 are formed to be transparent, since the first lightemitting unit 13A, the second light emitting unit 13B, the third lightemitting unit 13C, the first charge generating layer 14A, and the secondcharge generating layer 14B are also similarly transparent, it ispossible to manufacture a transparent organic EL element 10.

Note that the order of film formation does not have to start from thesecond electrode 12 side and may start from the first electrode 11 side.

The first light emitting unit 13A is formed of a first electrontransport layer 15A, a first light emitting layer 16A, and a first holetransport layer 17A. The second light emitting unit 13B is formed of asecond electron transport layer 15B, a second light emitting layer 16B,and a second hole transport layer 17B. The third light emitting unit 13Cis formed of a third electron transport layer 15C, a third lightemitting layer 16C, and a third hole transport layer 17C.

The first light emitting unit 13A, the second light emitting unit 13B,and the third light emitting unit 13C may employ any of variousstructures similar to those of conventionally-known organic EL elementsand may have any laminated structure as long as they include lightemitting layers made of at least an organic compound. For example, eachof the first light emitting unit 13A, the second light emitting unit13B, and the third light emitting unit 13C may be configured such thatan electron injection layer, a hole blocking layer, and the like arearranged on the first electrode 11 side of the light emitting layer anda hole injection layer, an electron blocking layer, and the like arearranged on the second electrode 12 side of the light emitting layer.

The electron transport layers are made of, for example, a conventionallywell-known electron transport material. In the organic EL element 10 ofthe embodiment, an electron transport material with a relatively deepHOMO (Highest Occupied Molecular Orbital) level is preferably used amongelectron transport materials generally used for organic EL elements.Specifically, an electron transport material with a HOMO level of atleast about 6.0 eV is preferably used. For example,4,7-Diphenyl-1,10-phenanthroline (Bphen),2,2′,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazol e) (TPBi),and the like can be used as such an electron transport material.

The electron injection layers are provided between the first electrode11 and the first electron transport layer 15A and between the firstcharge generating layer 14A and the second electron transport layer 15Bto improve injection efficiency of electrons from at least one of thefirst electrode 11 and the first charge generating layer 14A. Anelectron transport material having properties similar to the electrontransport layers can be used as the material of the electron injectionlayers. The electron transport layers and the electron injection layersare sometimes collectively referred to as electron transport layers.

The hole transport layers are made of, for example, a conventionallywell-known hole transport material. The hole transport material is notlimited to a particular material. For example, an organic compound(electron donating material) which has an ionization potential less than5.7 eV and which has a hole transport property, that is an electrondonating property is preferably used as the hole transport material. Forexample, an arylamine compound such as4,4′-bis-[N-(2-naphthyl)-N-phenyl-amino]biphenyl (α-NPD) or the like canbe used as the electron donating material.

The hole injection layers are provided between the second electrode 12and the second hole transport layer 17B and between the first chargegenerating layer 14A and the first hole transport layer 17A to improveinjection efficiency of holes from at least one of the second electrode12 and the first charge generating layer 14A. An electron donatingmaterial having properties similar to the hole transport layers can beused as the material of the hole injection layers. The hole transportlayers and the hole injection layers are sometimes collectively referredto as hole transport layers.

When the first light emitting unit 13A is the red/green light emittingunit, the light emitting layer included in the first light emitting unit13A is formed of a red phosphorescent light emitting layer and a greenphosphorescent light emitting layer. The red phosphorescent lightemitting layer and the green phosphorescent light emitting layer eachcontain a host material which is a main component and a guest materialwhich is a minor component as the organic compound. When the first lightemitting unit 13A is the red-green light emitting unit, the lightemitting layer included in the first light emitting unit 13A is formedof a mixed layer of a red phosphorescent material and a greenphosphorescent material. The mixed layer of the red phosphorescentmaterial and the green phosphorescent material contains a host materialwhich is a main component and a guest material which is a minorcomponent as the organic compound. The red phosphorescent material andthe green phosphorescent material correspond to the guest material outof these materials. In either case, emission of the red light and thegreen light is attributable particularly to the properties of the guestmaterial. Moreover, when the light emitting layer is formed of the mixedlayer of the red phosphorescent material and the green phosphorescentmaterial, it is important that light is efficiently emitted from bothlight emitting materials. To achieve this, it is effective to set theproportion of the red phosphorescent material lower than the proportionof the green phosphorescent material. This is due to the followingreason. Since the energy level of the red phosphorescent material islower than the energy level of the green phosphorescent material, energytransfer to the red phosphorescent material is more likely to occur.Accordingly, setting the proportion of the red phosphorescent materiallower than the proportion of the green phosphorescent material allowsboth of the red phosphorescent material and the green phosphorescentmaterial to efficiently emit light.

As the host material of the light emitting layer included in the firstlight emitting unit 13A, a material with an electron transport property,a material with a hole transport property, a material obtained by mixingthese materials, or the like can be used. Specifically, for example,4,4′-biscarbazolylbiphenyl (CBP),2,9-dimethyl-4,7-diphenyl-9,10-phenanthroline (BCP), or the like can beused as the host material of the phosphorescent light emitting layer.

The guest material of the light emitting layer included in the firstlight emitting unit 13A is also referred to as dopant material. Theguest material utilizing fluorescent light emission is generallyreferred to as fluorescent light emitting material. Alight emittinglayer made of the fluorescent light emitting material is referred to asfluorescent light emitting layer. Meanwhile, the guest materialutilizing phosphorescent light emission is generally referred to asphosphorescent light emitting material. A light emitting layer made ofthe phosphorescent light emitting material is referred to asphosphorescent light emitting layer.

In the phosphorescent light emitting layer out of these layers, it ispossible to utilize not only 75% of triplet excitons, which aregenerated by recombination of electrons and holes, but also 25% of thetriplet excitons, which are generated by energy transfer from singletexcitons. Accordingly, an internal quantum efficiency of 100% can beachieved in theory. Specifically, the excitons generated by therecombination of electrons and holes are converted to light in the lightemitting layer without thermal quenching or the like. In an organicmetal complex including heavy atoms such as iridium or platinum, aninternal quantum efficiency close to 100% is actually achieved byoptimization of the element structure and the like.

The guest material of the phosphorescent light emitting layer is notlimited to a particular material. For example, in the red phosphorescentlight emitting layer, a red phosphorescent light emitting material suchas Ir(piq)₃ and Ir(btpy)₃ can be used. Meanwhile, in the greenphosphorescent light emitting layer, a green phosphorescent lightemitting such as Ir(ppy)₃ can be used.

Each of the blue light emitting layers included in the second lightemitting unit 13B and the third light emitting unit 13C is formed of ablue fluorescent light emitting layer containing a blue fluorescentmaterial or a blue phosphorescent light emitting layer containing a bluephosphorescent material. Each blue light emitting layer contains a hostmaterial which is a main component and a guest material which is a minorcomponent as the organic compound. The blue fluorescent material or theblue phosphorescent material corresponds to the guest material out ofthese materials. In either case, emission of the blue light isattributable particularly to the properties of the guest material.

As the host material of the blue light emitting layers included in thesecond light emitting unit 13B and the third light emitting unit 13C, amaterial with an electron transport property, a material with a holetransport property, a material obtained by mixing these materials, orthe like can be used. In the blue fluorescent light emitting layers, forexample, a styryl derivative, an anthracene compound, a pyrene compound,or the like can be used. Meanwhile, in the blue phosphorescent lightemitting layer, for example, 4,4′-biscarbazolylbiphenyl (CBP),2,9-dimethyl-4,7-diphenyl-9,10-phenanthroline (BCP), or the like can beused.

As the guest material of the blue light emitting layers included in thesecond light emitting unit 13B and the third light emitting unit 13C, inthe blue fluorescent light emitting layer, for example, a styrylaminecompound, a fluoranthene compound, an aminopyrene compound, a boroncomplex, or the like can be used. Moreover, a material such as4,4′-bis[4-(diphenylamino)styryl]biphenyl (BDAVBi) or 2,7-bis{2-[phenyl(m-tolyl)amino]-9,9-dimethyl-fluoren-7-yl}-9,9-dimethyl-fluorene(MDP3FL) can be used. Meanwhile, in the blue phosphorescent lightemitting layer, for example, a blue phosphorescent light emittingmaterial such as Ir(Fppy)₃ can be used.

For example, a vacuum deposition method, a spin coating method, or thelike can be used as a film forming method of the layers forming thefirst light emitting unit 13A, the second light emitting unit 13B, andthe third light emitting unit 13C.

The first charge generating layer 14A and the second charge generatinglayer 14B are each formed of an electrically insulating layer made of anelectron accepting material and an electron donating material. Thespecific resistance of the electrically insulating layer is preferably1.0×10²Ω·cm or more, more preferably 1.0×10⁵Ω·cm or more.

Alternatively, the first charge generating layer 14A and the secondcharge generating layer 14B may each be configured such that the chargegenerating layer is formed of a mixed layer of different materials andone component of the mixed layer forms a charge transfer complex byredox. In this case, when voltage is applied between the first electrode11 and the second electrode 12, charges in the charge transfer complexmove to the first electrode 11 side and the second electrode 12 side. Inthe organic EL element 10, holes are thereby injected into the secondlight emitting unit 13B located on the first electrode 11 side of thesecond charge generating layer 14B and into the first light emittingunit 13A located on the first electrode 11 side of the first chargegenerating layer 14A. Moreover, in the organic EL element 10, electronsare injected into the third light emitting unit 13C located on thesecond electrode 12 side of the second charge generating layer 14B andinto the second light emitting unit 13B located on the second electrode12 side of the first charge generating layer 14A. Light can be therebysimultaneously emitted from the first light emitting unit 13A, thesecond light emitting unit 13B, and the third light emitting unit 13Cwith the same current amount. Accordingly, a current efficiency and anexternal quantum efficiency proportionate to the sum of luminousefficiencies of the first light emitting unit 13A, the second lightemitting unit 13B, and the third light emitting unit 13C can beobtained.

Alternatively, the first charge generating layer 14A and the secondcharge generating layer 14B may each be a laminate of an electronaccepting material and an electron donating material. In this case, whenvoltage is applied between the first electrode 11 and the secondelectrode 12, in an interface between the electron accepting materialand the electron donating material, charges generated by reactioninvolving electron transfer between these electron accepting materialand electron donating material move to the first electrode 11 side andthe second electrode 12 side. In the organic EL element 10, holes arethereby injected into the second light emitting unit 13B located on thefirst electrode 11 side of the second charge generating layer 14B andinto the first light emitting unit 13A located on the first electrode 11side of the first charge generating layer 14A. Moreover, in the organicEL element 10, electrons are injected into the third light emitting unit13C located on the second electrode 12 side of the second chargegenerating layer 14B and into the second light emitting unit 13B locatedon the second electrode 12 side of the first charge generating layer14A. Light can be thereby simultaneously emitted from the first lightemitting unit 13A, the second light emitting unit 13B, and the thirdlight emitting unit 13C with the same current amount. Accordingly, acurrent efficiency and an external quantum efficiency proportionate tothe sum of luminous efficiencies of the first light emitting unit 13A,the second light emitting unit 13B, and the third light emitting unit13C can be obtained.

For example, materials described in Japanese Patent ApplicationPublication No. 2003-272860 can be used as materials forming the firstcharge generating layer 14A and the second charge generating layer 14B.Among these, materials described in paragraphs [0019] to [0021] can bepreferably used. Alternatively, materials described in paragraphs [0023]to [0026] of “International Patent Application Publication No.WO2010/113493” can be used as materials forming the first chargegenerating layer 14A and the second charge generating layer 14B. Amongthese, a strong electron accepting material (HATCN6) described inparagraphs [0059] in particular can be preferably used. When substituentgroups represented by R in the structure expressed by the followingformula (1) are CN (cyano groups), this compound is HATCN6 describedabove.

where R represents an electron withdrawing group of F, Cl, Br, I, CN, orCF₃ (1)

FIG. 2 is a graph depicting an example of an emission spectrum of whitelight provided by the organic EL element 10 of the embodiment.

Specifically, as illustrated in FIG. 2, the white light provided by theorganic EL element 10 has an emission spectrum S continuous over thewavelength band of at least 380 nm to 780 nm as so-called visible light.

The emission spectrum. S has one peak wavelength p₁ in the redwavelength band R of 590 nm to 640 nm, one peak wavelength p₂ in thegreen wavelength band G of 500 nm to 560 nm, and one peak wavelength p₃or two peak wavelengths p₃, p₄ in the blue wavelength band B of 440 nmto 490 nm.

The blue light emitted by each blue light emitting layer is an importantfactor for obtaining white light with high color temperature.Specifically, it is desirable that, as illustrated in FIG. 2, theemission spectrum S has the one peak wavelength p₃ or the two peakwavelengths p₃, p₄ in the blue wavelength band B of 440 nm to 490 nm.

The organic EL element 10 of the embodiment can thereby provide whitelight with high color temperature. Moreover, in a conventional organicEL element, light emission in a low color temperature region such asincandescent lamp color is suitable for achieving highly-efficient lightemission and highly-efficient light emission is difficult to achieve ina color temperature equal to or higher than warm white which is higherthan the incandescent lamp color. Specifically, the maximum colortemperature of the incandescent lamp color (L) is 3250 K in chromaticityranges specified in “JIS Z 9112” and the organic EL element 10 of theembodiment can emit white light with correlated color temperature of3300 K or higher with high efficiency.

Moreover, it is desirable that the light emission intensities of thepeak wavelengths p₃, p₄ in the blue wavelength band B of 440 nm to 490nm are higher than either of the light emission intensity of the peakwavelength p₁ in the red wavelength band R of 590 to 640 nm and thelight emission intensity of the peak wavelength p₂ in the greenwavelength band G of 500 nm to 560 nm.

This can further increase the color temperature of the white light inthe organic EL element 10 of the embodiment. The organic EL element 10of the embodiment can provide white light with correlated colortemperature of 5000 K or higher.

Moreover, the position wavelength of the peak wavelength in the greenwavelength band of 500 nm to 560 nm is an important factor for obtainingwhite light with high luminous efficiency. Specifically, as illustratedin FIG. 2, the emission spectrum S desirably has the peak wavelength p₂around 540 nm in the green wavelength band G of 500 nm to 560 nm.

The organic EL element 10 of the embodiment can thereby provide whitelight with a high luminous efficiency. The organic EL element 10 of theembodiment can provide white light with an external quantum efficiencyof 20% or more.

Note that, when the position of the peak wavelength p₂ is on the shorterwavelength side of 540 nm, the luminous efficiency of the white lightdecreases together with a decrease in luminosity function. Meanwhile,when the position of the peak wavelength p₂ is on the longer wavelengthside of 540 nm, an amount of a green component of 550 nm to 600 nmincreases and a light emission ratio of a pure green component on theshort wavelength side thereby decreases. As a result, the colorrendering property becomes poor.

Moreover, it is desirable that, as illustrated in FIG. 2, the lightemission intensity of the peak wavelength p₂ in the green wavelengthband G of 500 nm to 560 nm is lower than the light emission intensity ofthe peak wavelength p₁ in the red wavelength band R of 590 to 640 nm andthe light emission intensities of the peak wavelengths p₃, p₄ in theblue wavelength band B of 440 nm to 490 nm.

The organic EL element 10 of the embodiment can be thereby furtherimproved in the luminous efficiency of the white light. The organic ELelement 10 of the embodiment can provide white light with an externalquantum efficiency of 30% or more.

Note that, when the light emission intensity of the peak wavelength p₂in the green wavelength band G of 500 nm to 560 nm is increased relativeto the light emission intensity of the peak wavelength p₁ in the redwavelength band R of 590 to 640 nm and the light emission intensities ofthe peak wavelengths p₃, p₄ in the blue wavelength band B of 440 nm to490 nm, the light emission intensity of a blue component relativelydecreases and the color temperature thereby decreases.

Moreover, presence of a bottom wavelength in a wavelength band of 550 nmto 600 nm is an important factor for obtaining white light with anexcellent color rendering property. Specifically, as illustrated in FIG.2, the emission spectrum S desirably has one bottom wavelength b₁ in thewavelength band of 550 nm to 600 nm.

The organic EL element 10 of the embodiment can thereby provide whitelight with an excellent color rendering property. The organic EL element10 of the embodiment can provide white light in which the average colorrendering index (Ra) is 70 or more and R6 and R12 among the specialcolor rendering indices (Ri) are 60 or more and 30 or more,respectively.

Table 1 and FIGS. 3 and 4 depict results of simulation verifying theeffects on R6 and R12 in a white element.

This simulation was performed such that the green and red light emissionintensities were fixed to 1.0 in a three (blue, green, andred)-wavelength white element and numerical values were standardized bydividing the spectral intensity of the white light by the red peakwavelength intensity, the white light obtained with the light emissionintensity of the blue spectrum set to a certain ratio. Moreover, variouscharacteristic values were calculated with the light emission intensityof the blue spectrum varied at a certain ratio. The green and red lightemission intensities were fixed to 1.0 to quantitatively evaluate theeffects of the blue light emission on R6 and R12.

TABLE 1 Spectrum No. 1 2 3 4 5 6 7 8 9 Blue (450 nm) light 0.120 0.2370.355 0.472 0.589 0.763 0.936 1.108 1.280 emission intensity CCT (K) — —3630 3860 4100 4530 5000 5520 6140 Deviation duv 0.0247 0.0202 0.01660.0134 0.0107 0.0075 0.0053 0.0037 0.0032 Ra 61 64 68 71 73 77 80 83 85R6 54 61 67 72 76 82 87 91 93 R12 6 18 29 38 46 54 60 70 72

“Blue (450 nm) light emission intensity” in Table 1 refers to the lightemission intensity at 450 nm which is the peak wavelength in the bluespectrum.

FIG. 3 illustrates white spectra calculated by simulation performed withthe intensity of the blue spectrum varied.

The blue spectrum, the green spectrum, and the red spectrum used in thesimulation have the same wavelengths and waveforms as those of theemission spectrum of Example 1 to be described later.

It is found from Table 1 and FIG. 4 that the higher the blue lightemission intensity is, the greater the values of Ra, R6, and R12 are.

In the spectrum No. 1 in which R6 is lower than 60, the value of thedeviation duv is 0.02 or higher. Accordingly, the spectrum No. 1 haslight emission color to which the definition of correlated colortemperature cannot be applied.

In each of the spectrum No. 2 and the spectrum No. 3, although R6 is 60or higher, the value of R12 is below 30 and the value of the deviationduv is thus high. The spectrum No. 2 has light emission color to whichthe definition of correlated color temperature cannot be applied likethe spectrum No. 1. Moreover, the spectrum No. 3 also greatly deviatesfrom the black body radiation and emission of white light with goodcolor cannot be achieved.

Meanwhile, in the spectra No. 4 to No. 9 which satisfy the conditions ofR6 being 60 or more and R12 being 30 or more, emission of white lightwith a low value of deviation duv and an excellent color renderingproperty can be achieved. The deviation duv is preferably within a rangeof −0.015 to +0.015, more preferably within a range of −0.01 to +0.01.

Moreover, in the spectra No. 7 to No. 9 in which the value of R12 is 60or more, light emission with higher color temperature and a better colorrendering property than those in No. 4 to No. 6 is achieved and thevalues of the deviation duv are also small. Accordingly, emission ofwhite light with an excellent color rendering property and high colortemperature in particular are achieved.

Moreover, Table 2 and FIGS. 5 and 6 depict results of simulationverifying effects on R6 and R12 in a white element.

This simulation was performed such that the blue and red light emissionintensities were fixed to 1.0 in a three (blue, green, andred)-wavelength white element and numerical values were standardized bydividing the spectral intensity of the white light by the blue peakwavelength intensity, the white light obtained with the light emissionintensity of the green spectrum set to a certain ratio. Moreover,various characteristic values were calculated with the light emissionintensity of the blue spectrum varied at a certain ratio. The blue andred light emission intensities were fixed to 1.0 to quantitativelyevaluate the effects of green light emission on R6 and R12.

Moreover, in FIG. 5, when the light emission intensity of the greenspectrum is changed, the intensity of the red spectrum is also changed.This is because the peak wavelengths in the green spectrum and the redspectrum are close to each other and the light emission intensity in atail portion of the green spectrum affects the light emission intensityof the red spectrum.

As illustrated in the spectrum. No. 5 of FIG. 5, the light emissionintensity of the peak wavelength in the green wavelength band of 500 nmto 560 nm is lower than the light emission intensity of the peakwavelength in the blue wavelength band of 440 nm to 490 nm and the lightemission intensity of the peak wavelength in the red wavelength band of590 nm to 640 nm.

Moreover, as illustrated in the spectrum No. 5 of FIG. 5, the ratio ofthe light emission intensity of the peak wavelength in the greenwavelength band of 500 nm to 560 nm to the light emission intensity ofthe peak wavelength in the red wavelength band of 590 nm to 640 nm is0.9 or less.

TABLE 2 Spectrum No. 1 2 3 4 5 Green 1.180 1.136 1.037 0.993 0.934 (544nm) light emission intensity CCT (K) 4650 4750 4850 4930 5020 duv 0.01220.008 0.0023 −0.0001 −0.0034 Ra 77 81 86 88 90 R6 78 84 91 93 93 R12 4856 65 69 78

“Green (544 nm) light emission intensity” in table 2 refers to the lightemission intensity at 544 nm which is the peak wavelength in the greenspectrum.

FIG. 5 illustrates white spectra calculated by simulation performed withthe intensity of the blue spectrum varied.

The blue spectrum, the green spectrum, and the red spectrum used in thesimulation have the same wavelengths and waveforms as those of theemission spectrum of Example 1 to be described later.

It is found from Table 2 and FIG. 6 that the lower the green lightemission intensity is, the greater the values of Ra, R6, and R12 are.Accordingly, it is found that the color rendering property can beimproved by reducing the green light emission intensity in addition tothe method of increasing the light emission intensity of the bluespectrum described in [0052] to [0056].

Moreover, in the organic EL element 10 of the embodiment, as illustratedin FIG. 2, the emission spectrum. S desirably has one bottom wavelengthb₂ between the two peak wavelengths p₂, p₃ adjacent to each other in theblue wavelength band B and the green wavelength band G of 500 nm to 520nm.

The luminous efficiency and the color rendering property of the whitelight can be thereby optimized at the same time by preferablycontrolling the ratio between the light emission intensities of the peakwavelengths p₂, p₃.

Moreover, in the organic EL element 10 of the embodiment, as illustratedin FIG. 2, the light emission intensity of the one bottom wavelength b₂in the blue wavelength band B and the green wavelength band G of 500 nmto 520 nm is preferably lower than the light emission intensities of thebottom wavelengths b₁, b₃ in the wavelength band (green wavelength bandG or red wavelength band R) of 570 nm to 590 nm.

The color temperature of the white light can be thereby optimized byappropriately controlling the light emission intensity ratio betweenpeak wavelengths p₁ and p₂ forming the bottom wavelength b₁ and thelight emission intensity ratio between the peak wavelengths p₃ and p₄forming the bottom wavelength b₃.

Moreover, in the organic EL element 10 of the embodiment, as illustratedin FIG. 2, a ratio of (B) to (A) ((B)/(A)) is preferably 0.50 orsmaller, where (A) is the light emission intensity of the peakwavelength having the highest light emission intensity (peak wavelengthp₁ in FIG. 2) and (B) is the light emission intensity of the one bottomwavelength b₁ in the blue wavelength band B and the green wavelengthband G of 500 nm to 520 nm.

The color temperature and the color rendering property of the whitelight can be thereby optimized at the same time.

As described above, the organic EL element 10 of the embodiment canprovide white light with high color temperature, high luminousefficiency, and an excellent color rendering property. Moreover, sincethe organic EL element 10 of the embodiment has the MPE structure inwhich the first light emitting unit 13A, the second light emitting unit13B, and the third light emitting unit 13C are stacked one on top ofanother with each of the first charge generating layer 14A and thesecond charge generating layer 14B sandwiched between the correspondingpair of adjacent light emitting units, the organic EL element 10 canprovide the white light while achieving high-luminance light emissionand long-life driving.

The organic EL element 10 of the embodiment can be thus preferably usedin both of a display device and a lighting device.

Second Embodiment

FIG. 7 is a cross-sectional view illustrating a schematic configurationof a second embodiment of the organic EL element in the presentinvention.

As illustrated in FIG. 7, the organic EL element 20 of the embodimenthas a structure in which multiple light emitting units 23A, 23B, 23Ceach including a light emitting layer made of at least an organiccompound are stacked one on top of another between a first electrode 21and a second electrode 22 with each of charge generating layers (CGL)24A, 24B sandwiched between a corresponding pair of the adjacent lightemitting units. The organic EL element 20 is an organic EL elementcapable of providing white light by causing the multiple light emittingunits 23A, 23B, 23C to emit light.

The organic EL element 20 of the embodiment includes the first lightemitting unit 23A, the second light emitting unit 23B, and the thirdlight emitting unit 23C.

The first light emitting unit 23A is a blue light emitting unit. Theblue light emitting unit includes a light emitting layer formed of ablue light emitting layer which emits blue light with one or two peakwavelengths in the blue wavelength band. The blue light emitting layermay be a blue fluorescent light emitting layer containing a bluefluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light provided bythe blue light emitting unit including the blue fluorescent lightemitting layer may include a delayed fluorescence component.

The second light emitting unit 23B is a red/green light emitting unit ora red-green light emitting unit. The red/green light emitting unitincludes a light emitting layer formed of a red phosphorescent lightemitting layer which emits red light with one peak wavelength in a redwavelength band and a green phosphorescent light emitting layer whichemits green light with one or two peak wavelengths in a green wavelengthband. Specifically, the red/green light emitting unit is a layer formedby stacking the red phosphorescent light emitting layer and the greenphosphorescent light emitting layer one on top of the other. Thered-green light emitting unit includes alight emitting layer formed of amixed layer of a red phosphorescent material and a green phosphorescentmaterial. Specifically, the red-green light emitting unit is one layer(single layer) containing the red phosphorescent material and the greenphosphorescent material.

The third light emitting unit 23C is a blue light emitting unit. Theblue light emitting unit includes a light emitting layer formed of ablue light emitting layer which emits blue light with one or two peakwavelengths in a blue wavelength band. The blue light emitting layer maybe a blue fluorescent light emitting layer containing a blue fluorescentmaterial or a blue phosphorescent light emitting layer containing a bluephosphorescent material. The blue light provided by the blue lightemitting unit including the blue fluorescent light emitting layer mayinclude a delayed fluorescence component.

The first light emitting unit 23A and the second light emitting unit 23Bare stacked one on top of the other with the first charge generatinglayer 24A sandwiched therebetween.

The second light emitting unit 23B and the third light emitting unit 23Care stacked one on top of the other with the second charge generatinglayer 24B sandwiched therebetween.

The organic EL element 20 of the embodiment has a structure in which thesecond electrode 22, the third light emitting unit 23C, the secondcharge generating layer 24B, the second light emitting unit 23B, thefirst charge generating layer 24A, the first light emitting unit 23A,and the first electrode 21 are stacked one on top of another in thisorder. Specifically, the organic EL element 20 of the embodiment has anMPE structure in which the first light emitting unit 23A, the secondlight emitting unit 23B, and the third light emitting unit 23C arestacked one on top of another with each of the first charge generatinglayer 24A and the second charge generating layer 24B sandwiched betweenthe corresponding pair of adjacent light emitting units.

In the organic EL element 20 of the embodiment, the white light producedby light emission of the first light emitting unit 23A, the second lightemitting unit 23B, and the third light emitting unit 23C has an emissionspectrum continuous over a wavelength band of at least 380 nm to 780 nm.Moreover, in the organic EL element 20 of the embodiment, the whitelight has one or two peak wavelengths in the blue wavelength band of 440nm to 490 nm in this emission spectrum. Furthermore, in the organic ELelement 20 of the embodiment, the white light has one peak wavelength inthe red wavelength band of 590 nm to 640 nm and one or two peakwavelengths in the green wavelength band of 500 nm to 560 nm in thisemission spectrum.

The same electrode as the first electrode 11 in the aforementioned firstembodiment can be used as the first electrode 21.

The same electrode as the second electrode 12 in the aforementionedfirst embodiment can be used as the second electrode 22.

The first light emitting unit 23A is formed of a first electrontransport layer 25A, a first light emitting layer 26A, and a first holetransport layer 27A. The second light emitting unit 23B is formed of asecond electron transport layer 25B, a second light emitting layer 26B,and a second hole transport layer 27B. The third light emitting unit 23Cis formed of a third electron transport layer 25C, a third lightemitting layer 26C, and a third hole transport layer 27C.

The first light emitting unit 23A, the second light emitting unit 23B,and the third light emitting unit 23C may employ any of variousstructures similar to those of conventionally-known organic EL elementsand may have any laminated structure as long as they include lightemitting layers made of at least an organic compound. For example, eachof the first light emitting unit 23A, the second light emitting unit23B, and the third light emitting unit 23C may be configured such thatan electron injection layer, a hole blocking layer, and the like arearranged on the first electrode 21 side of the light emitting layer anda hole injection layer, an electron blocking layer, and the like arearranged on the second electrode 22 side of the light emitting layer.

The electron transport layers have the same configuration as that of theelectron transport layers in the aforementioned first embodiment.

The hole transport layers have the same configuration as that of thehole transport layers in the aforementioned first embodiment.

Each of the blue light emitting layers included in the first lightemitting unit 23A and the third light emitting unit 23C is formed of ablue fluorescent light emitting layer containing a blue fluorescentmaterial or a blue phosphorescent light emitting layer containing a bluephosphorescent material. Each blue light emitting layer contains a hostmaterial which is a main component and a guest material which is a minorcomponent as the organic compound. The blue fluorescent material or theblue phosphorescent material corresponds to the guest material out ofthese materials. In either case, emission of the blue light isattributable particularly to the properties of the guest material.

As the host material of the blue light emitting layers included in thefirst light emitting unit 23A and the third light emitting unit 23C, thesame material as the host material of the blue light emitting layers inthe aforementioned first embodiment can be used.

As the guest material of the blue light emitting layers included in thefirst light emitting unit 23A and the third light emitting unit 23C, thesame material as the guest material of the blue light emitting layers inthe aforementioned first embodiment can be used.

When the second light emitting unit 23B is the red/green light emittingunit, the light emitting layer included in the second light emittingunit 23B is formed of a red phosphorescent light emitting layer and agreen phosphorescent light emitting layer. The red phosphorescent lightemitting layer and the green phosphorescent light emitting layer eachcontain a host material which is a main component and a guest materialwhich is a minor component as the organic compound. When the secondlight emitting unit 23B is the red-green light emitting unit, the lightemitting layer included in the second light emitting unit 23B is formedof a mixed layer of a red phosphorescent material and a greenphosphorescent material. The mixed layer of the red phosphorescentmaterial and the green phosphorescent material contains a host materialwhich is a main component and a guest material which is a minorcomponent as the organic compound. The red phosphorescent material andthe green phosphorescent material correspond to the guest material outof these materials. In either case, emission of the red light and thegreen light is attributable particularly to the properties of the guestmaterial. Moreover, when the light emitting layer is formed of the mixedlayer of the red phosphorescent material and the green phosphorescentmaterial, it is important that light is efficiently emitted from bothlight emitting materials. To achieve this, it is effective to set theproportion of the red phosphorescent material lower than the proportionof the green phosphorescent material. This is due to the followingreason. Since the energy level of the red phosphorescent material islower than the energy level of the green phosphorescent material, energytransfer to the red phosphorescent material is more likely to occur.Accordingly, setting the proportion of the red phosphorescent materiallower than the proportion of the green phosphorescent material allowsboth of the red phosphorescent material and the green phosphorescentmaterial to efficiently emit light.

As the host material of the light emitting layer included in the secondlight emitting unit 23B, the same material as the host material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

As the guest material of the light emitting layer included in the secondlight emitting unit 23B, the same material as the guest material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

For example, a vacuum deposition method, a spin coating method, or thelike can be used as a film forming method of the layers forming thefirst light emitting unit 23A, the second light emitting unit 23B, andthe third light emitting unit 23C.

The first charge generating layer 24A and the second charge generatinglayer 24B are each formed of an electrically insulating layer made of anelectron accepting material and an electron donating material. Thespecific resistance of the electrically insulating layer is preferably1.0×10²Ω·cm or more, more preferably 1.0×10⁵Ω·cm or more.

Alternatively, the first charge generating layer 24A and the secondcharge generating layer 24B may each be configured such that the chargegenerating layer is formed of a mixed layer of different materials andone component of the mixed layer forms a charge transfer complex byredox. In this case, when voltage is applied between the first electrode21 and the second electrode 22, charges in the charge transfer complexmove to the first electrode 21 side and the second electrode 22 side. Inthe organic EL element 20, holes are thereby injected into the secondlight emitting unit 23B located on the first electrode 21 side of thesecond charge generating layer 24B and into the first light emittingunit 23A located on the first electrode 21 side of the first chargegenerating layer 24A. Moreover, in the organic EL element 20, electronsare injected into the third light emitting unit 23C located on thesecond electrode 22 side of the second charge generating layer 24B andinto the second light emitting unit 23B located on the second electrode22 side of the first charge generating layer 24A. Light can be therebysimultaneously emitted from the first light emitting unit 23A, thesecond light emitting unit 23B, and the third light emitting unit 23Cwith the same current amount. Accordingly, a current efficiency and anexternal quantum efficiency proportionate to the sum of luminousefficiencies of the first light emitting unit 23A, the second lightemitting unit 23B, and the third light emitting unit 23C can beobtained.

Alternatively, the first charge generating layer 24A and the secondcharge generating layer 24B may each be a laminate of an electronaccepting material and an electron donating material. In this case, whenvoltage is applied between the first electrode 21 and the secondelectrode 22, in an interface between the electron accepting materialand the electron donating material, charges generated by reactioninvolving electron transfer between these electron accepting materialand electron donating material move to the first electrode 21 side andthe second electrode 22 side. In the organic EL element 20, holes arethereby injected into the second light emitting unit 23B located on thefirst electrode 21 side of the second charge generating layer 24B andinto the first light emitting unit 23A located on the first electrode 21side of the first charge generating layer 24A. Moreover, in the organicEL element 20, electrons are injected into the third light emitting unit23C located on the second electrode 22 side of the second chargegenerating layer 24B and into the second light emitting unit 23B locatedon the second electrode 22 side of the first charge generating layer24A. Light can be thereby simultaneously emitted from the first lightemitting unit 23A, the second light emitting unit 23B, and the thirdlight emitting unit 23C with the same current amount. Accordingly, acurrent efficiency and an external quantum efficiency proportionate tothe sum of luminous efficiencies of the first light emitting unit 23A,the second light emitting unit 23B, and the third light emitting unit23C can be obtained.

As materials forming the first charge generating layer 24A and thesecond charge generating layer 24B, the same materials as the materialsforming the first charge generating layer 14A and the second chargegenerating layer 14B in the aforementioned first embodiment can be used.

The organic EL element 20 having the structure described above canprovide white light by causing the first light emitting unit 23A, thesecond light emitting unit 23B, and the third light emitting unit 23C toemit light.

Moreover, the organic EL element 20 of the embodiment can provide whitelight with high color temperature, high luminous efficiency, and anexcellent color rendering property as in the organic EL element 10 inthe aforementioned first embodiment. Moreover, the organic EL element 20of the embodiment has the MPE structure in which the first lightemitting unit 23A, the second light emitting unit 23B, and the thirdlight emitting unit 23C are stacked one on top of another with each ofthe first charge generating layer 24A and the second charge generatinglayer 24B sandwiched between the corresponding pair of adjacent lightemitting units. Accordingly, the organic EL element 20 can provide thewhite light while achieving high-luminance light emission and long-lifedriving.

The organic EL element 20 of the embodiment can be thus preferably usedin both of a display device and a lighting device.

Third Embodiment

FIG. 8 is a cross-sectional view illustrating a schematic configurationof a third embodiment of the organic EL element in the presentinvention.

As illustrated in FIG. 8, the organic EL element 30 of the embodimenthas a structure in which multiple light emitting units 33A, 33B, 33C,33D each including a light emitting layer made of at least an organiccompound are stacked one on top of another between a first electrode 31and a second electrode 32 with each of charge generating layers (CGL)34A, 34B, 34C sandwiched between a corresponding pair of the adjacentlight emitting units. The organic EL element 30 is an organic EL elementcapable of providing white light by causing the multiple light emittingunits 33A, 33B, 33C, 33D to emit light.

The organic EL element 30 of the embodiment includes the first lightemitting unit 33A, the second light emitting unit 33B, the third lightemitting unit 33C, and the fourth light emitting unit 33D.

The first light emitting unit 33A is a red/green light emitting unit ora red-green light emitting unit. The red/green light emitting unitincludes a light emitting layer formed of a red phosphorescent lightemitting layer which emits red light with one peak wavelength in a redwavelength band and a green phosphorescent light emitting layer whichemits green light with one or two peak wavelengths in a green wavelengthband. Specifically, the red/green light emitting unit is a layer formedby stacking the red phosphorescent light emitting layer and the greenphosphorescent light emitting layer one on top of the other. Thered-green light emitting unit includes alight emitting layer formed of amixed layer of a red phosphorescent material and a green phosphorescentmaterial. Specifically, the red-green light emitting unit is one layer(single layer) containing the red phosphorescent material and the greenphosphorescent material.

The second light emitting unit 33B is a blue light emitting unit. Theblue light emitting unit includes a light emitting layer formed of ablue light emitting layer which emits blue light with one or two peakwavelengths in the blue wavelength band. The blue light emitting layermay be a blue fluorescent light emitting layer containing a bluefluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light provided bythe blue light emitting unit including the blue fluorescent lightemitting layer may include a delayed fluorescence component.

The third light emitting unit 33C is a red/green light emitting unit ora red-green light emitting unit. The red/green light emitting unitincludes a light emitting layer formed of a red phosphorescent lightemitting layer which emits red light with one peak wavelength in a redwavelength band and a green phosphorescent light emitting layer whichemits green light with one or two peak wavelengths in a green wavelengthband. Specifically, the red/green light emitting unit is a layer formedby stacking the red phosphorescent light emitting layer and the greenphosphorescent light emitting layer one on top of the other. Thered-green light emitting unit includes alight emitting layer formed of amixed layer of a red phosphorescent material and a green phosphorescentmaterial. Specifically, the red-green light emitting unit is one layer(single layer) containing the red phosphorescent material and the greenphosphorescent material.

The fourth light emitting unit 33D is a blue light emitting unit. Theblue light emitting unit includes a light emitting layer formed of ablue light emitting layer which emits blue light with one or two peakwavelengths in the blue wavelength band. The blue light emitting layermay be a blue fluorescent light emitting layer containing a bluefluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light provided bythe blue light emitting unit including the blue fluorescent lightemitting layer may include a delayed fluorescence component.

The first light emitting unit 33A and the second light emitting unit 33Bare stacked one on top of the other with the first charge generatinglayer 34A sandwiched therebetween.

The second light emitting unit 33B and the third light emitting unit 33Care stacked one on top of the other with the second charge generatinglayer 34B sandwiched therebetween.

The third light emitting unit 33C and the fourth light emitting unit 33Dare stacked one on top of the other with the third charge generatinglayer 34C sandwiched therebetween.

The organic EL element 30 of the embodiment has a structure in which thesecond electrode 32, the fourth light emitting unit 33D, the thirdcharge generating layer 34C, the third light emitting unit 33C, thesecond charge generating layer 34B, the second light emitting unit 33B,the first charge generating layer 34A, the first light emitting unit33A, and the first electrode 31 are stacked one on top of another inthis order. Specifically, the organic EL element 30 of the embodimenthas an MPE structure in which the first light emitting unit 33A, thesecond light emitting unit 33B, the third light emitting unit 33C, andthe fourth light emitting unit 33D are stacked one on top of anotherwith each of the first charge generating layer 34A, the second chargegenerating layer 34B, and the third charge generating layer 34Csandwiched between the corresponding pair of adjacent light emittingunits.

In the organic EL element 30 of the embodiment, the white light producedby light emission of the first light emitting unit 33A, the second lightemitting unit 33B, the third light emitting unit 33C, and the fourthlight emitting unit 33D has an emission spectrum continuous over awavelength band of at least 380 nm to 780 nm. Moreover, in the organicEL element 30 of the embodiment, the white light has one or two peakwavelengths in the blue wavelength band of 440 nm to 490 nm in thisemission spectrum. Furthermore, in the organic EL element 30 of theembodiment, the white light has one peak wavelength in the redwavelength band of 590 nm to 640 nm and one or two peak wavelengths inthe green wavelength band of 500 nm to 560 nm in this emission spectrum.

The same electrode as the first electrode 11 in the aforementioned firstembodiment can be used as the first electrode 31.

The same electrode as the second electrode 12 in the aforementionedfirst embodiment can be used as the second electrode 32.

The first light emitting unit 33A is formed of a first electrontransport layer 35A, a first light emitting layer 36A, and a first holetransport layer 37A. The second light emitting unit 33B is formed of asecond electron transport layer 35B, a second light emitting layer 36B,and a second hole transport layer 37B. The third light emitting unit 33Cis formed of a third electron transport layer 35C, a third lightemitting layer 36C, and a third hole transport layer 37C. The fourthlight emitting unit 33D is formed of a fourth electron transport layer35D, a fourth light emitting layer 36D, and a fourth hole transportlayer 37D.

The first light emitting unit 33A, the second light emitting unit 33B,the third light emitting unit 33C, and the fourth light emitting unit33D may employ any of various structures similar to those ofconventionally-known organic EL elements and may have any laminatedstructure as long as they include light emitting layers made of at leastan organic compound. For example, each of the first light emitting unit33A, the second light emitting unit 33B, the third light emitting unit33C, and the fourth light emitting unit 33D may be configured such thatan electron injection layer, a hole blocking layer, and the like arearranged on the first electrode 31 side of the light emitting layer anda hole injection layer, an electron blocking layer, and the like arearranged on the second electrode 32 side of the light emitting layer.

The electron transport layers have the same configuration as that of theelectron transport layers in the aforementioned first embodiment.

The hole transport layers have the same configuration as that of thehole transport layers in the aforementioned first embodiment.

When the first light emitting unit 33A is the red/green light emittingunit, the light emitting layer included in the first light emitting unit33A is formed of a red phosphorescent light emitting layer and a greenphosphorescent light emitting layer. The red phosphorescent lightemitting layer and the green phosphorescent light emitting layer eachcontain a host material which is a main component and a guest materialwhich is a minor component as the organic compound. When the first lightemitting unit 33A is the red-green light emitting unit, the lightemitting layer included in the first light emitting unit 33A is formedof a mixed layer of a red phosphorescent material and a greenphosphorescent material. The mixed layer of the red phosphorescentmaterial and the green phosphorescent material contains a host materialwhich is a main component and a guest material which is a minorcomponent as the organic compound. The red phosphorescent material andthe green phosphorescent material correspond to the guest material outof these materials. In either case, emission of the red light and thegreen light is attributable particularly to the properties of the guestmaterial. Moreover, when the light emitting layer is formed of the mixedlayer of the red phosphorescent material and the green phosphorescentmaterial, it is important that light is efficiently emitted from bothlight emitting materials. To achieve this, it is effective to set theproportion of the red phosphorescent material lower than the proportionof the green phosphorescent material. This is due to the followingreason. Since the energy level of the red phosphorescent material islower than the energy level of the green phosphorescent material, energytransfer to the red phosphorescent material is more likely to occur.Accordingly, setting the proportion of the red phosphorescent materiallower than the proportion of the green phosphorescent material allowsboth of the red phosphorescent material and the green phosphorescentmaterial to efficiently emit light.

As the host material of the light emitting layer included in the firstlight emitting unit 33A, the same material as the host material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

As the guest material of the light emitting layer included in the firstlight emitting unit 33A, the same material as the guest material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

The blue light emitting layer included in the second light emitting unit33B is formed of a blue fluorescent light emitting layer containing ablue fluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light emitting layercontains a host material which is a main component and a guest materialwhich is a minor component as the organic compound. The blue fluorescentmaterial or the blue phosphorescent material corresponds to the guestmaterial out of these materials. In either case, emission of the bluelight is attributable particularly to the properties of the guestmaterial.

As the host material of the blue light emitting layer included in thesecond light emitting unit 33B, the same material as the host materialof the blue light emitting layers in the aforementioned first embodimentcan be used.

As the guest material of the blue light emitting layer included in thesecond light emitting unit 33B, the same material as the guest materialof the blue light emitting layers in the aforementioned first embodimentcan be used.

When the third light emitting unit 33C is the red/green light emittingunit, the light emitting layer included in the third light emitting unit33C is formed of a red phosphorescent light emitting layer and a greenphosphorescent light emitting layer. The red phosphorescent lightemitting layer and the green phosphorescent light emitting layer eachcontain a host material which is a main component and a guest materialwhich is a minor component as the organic compound. When the third lightemitting unit 33C is the red-green light emitting unit, the lightemitting layer included in the third light emitting unit 33C is formedof a mixed layer of a red phosphorescent material and a greenphosphorescent material. The mixed layer of the red phosphorescentmaterial and the green phosphorescent material contains a host materialwhich is a main component and a guest material which is a minorcomponent as the organic compound. The red phosphorescent material andthe green phosphorescent material correspond to the guest material outof these materials. In either case, emission of the red light and thegreen light is attributable particularly to the properties of the guestmaterial. Moreover, when the light emitting layer is formed of the mixedlayer of the red phosphorescent material and the green phosphorescentmaterial, it is important that light is efficiently emitted from bothlight emitting materials. To achieve this, it is effective to set theproportion of the red phosphorescent material lower than the proportionof the green phosphorescent material. This is due to the followingreason. Since the energy level of the red phosphorescent material islower than the energy level of the green phosphorescent material, energytransfer to the red phosphorescent material is more likely to occur.Accordingly, setting the proportion of the red phosphorescent materiallower than the proportion of the green phosphorescent material allowsboth of the red phosphorescent material and the green phosphorescentmaterial to efficiently emit light.

As the host material of the light emitting layer included in the thirdlight emitting unit 33C, the same material as the host material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

As the guest material of the light emitting layer included in the thirdlight emitting unit 33C, the same material as the guest material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

The blue light emitting layer included in the fourth light emitting unit33D is formed of a blue fluorescent light emitting layer containing ablue fluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light emitting layercontains a host material which is a main component and a guest materialwhich is a minor component as the organic compound. The blue fluorescentmaterial or the blue phosphorescent material corresponds to the guestmaterial out of these materials. In either case, emission of the bluelight is attributable particularly to the properties of the guestmaterial.

As the host material of the blue light emitting layer included in thefourth light emitting unit 33D, the same material as the host materialof the blue light emitting layers in the aforementioned first embodimentcan be used.

As the guest material of the blue light emitting layer included in thefourth light emitting unit 33D, the same material as the guest materialof the blue light emitting layers in the aforementioned first embodimentcan be used.

For example, a vacuum deposition method, a spin coating method, or thelike can be used as a film forming method of the layers forming thefirst light emitting unit 33A, the second light emitting unit 33B, thethird light emitting unit 33C, and the fourth light emitting unit 33D.

The first charge generating layer 34A, the second charge generatinglayer 34B, and the third charge generating layer 34C are each formed ofan electrically insulating layer made of an electron accepting materialand an electron donating material. The specific resistance of theelectrically insulating layer is preferably 1.0×10²Ω·cm or more, morepreferably 1.0×10⁵Ω·cm or more.

Alternatively, the first charge generating layer 34A, the second chargegenerating layer 34B, and the third charge generating layer 34C may eachbe configured such that the charge generating layer is formed of a mixedlayer of different materials and one component of the mixed layer formsa charge transfer complex by redox. In this case, when voltage isapplied between the first electrode 31 and the second electrode 32,charges in the charge transfer complex move to the first electrode 31side and the second electrode 32 side. Holes are thereby injected intothe third light emitting unit 33C located on the first electrode 31 sideof the third charge generating layer 34C, the second light emitting unit33B located on the first electrode 31 side of the second chargegenerating layer 34B, and the first light emitting unit 33A located onthe first electrode 31 side of the first charge generating layer 34A.Moreover, electrons are injected into the fourth light emitting unit 33Dlocated on the second electrode 32 side of the third charge generatinglayer 34C, the third light emitting unit 33C located on the secondelectrode 32 side of the second charge generating layer 34B, and thesecond light emitting unit 33B located on the second electrode 32 sideof the first charge generating layer 34A. Light can be therebysimultaneously emitted from the first light emitting unit 33A, thesecond light emitting unit 33B, the third light emitting unit 33C, andthe fourth light emitting unit 33D with the same current amount.Accordingly, a current efficiency and an external quantum efficiencyproportionate to the sum of luminous efficiencies of the first lightemitting unit 33A, the second light emitting unit 33B, the third lightemitting unit 33C, and the fourth light emitting unit 33D can beobtained.

Alternatively, the first charge generating layer 34A, the second chargegenerating layer 34B, and the third charge generating layer 34C may eachbe a laminate of an electron accepting material and an electron donatingmaterial. In this case, when voltage is applied between the firstelectrode 31 and the second electrode 32, in an interface between theelectron accepting material and the electron donating material, chargesgenerated by reaction involving electron transfer between these electronaccepting material and electron donating material move to the firstelectrode 31 side and the second electrode 32 side. In the organic ELelement 30, holes are thereby injected into the third light emittingunit 33C located on the first electrode 31 side of the third chargegenerating layer 34C, the second light emitting unit 33B located on thefirst electrode 31 side of the second charge generating layer 34B, andthe first light emitting unit 33A located on the first electrode 31 sideof the first charge generating layer 34A. Moreover, in the organic ELelement 30, electrons are injected into the fourth light emitting unit33D located on the second electrode 32 side of the third chargegenerating layer 34C, the third light emitting unit 33C located on thesecond electrode 32 side of the second charge generating layer 34B, andthe second light emitting unit 33B located on the second electrode 32side of the first charge generating layer 34A. Light can be therebysimultaneously emitted from the first light emitting unit 33A, thesecond light emitting unit 33B, the third light emitting unit 33C, andthe fourth light emitting unit 33D with the same current amount.Accordingly, a current efficiency and an external quantum efficiencyproportionate to the sum of luminous efficiencies of the first lightemitting unit 33A, the second light emitting unit 33B, the third lightemitting unit 33C, and the fourth light emitting unit 33D can beobtained.

As materials forming the first charge generating layer 34A, the secondcharge generating layer 34B, and the third charge generating layer 34C,the same materials as the materials forming the first charge generatinglayer 14A and the second charge generating layer 14B in theaforementioned first embodiment can be used.

The organic EL element 30 having the structure described above canprovide white light by causing the first light emitting unit 33A, thesecond light emitting unit 33B, the third light emitting unit 33C, andthe fourth light emitting unit 33D to emit light.

Moreover, the organic EL element 30 of the embodiment can provide whitelight with high color temperature, high luminous efficiency, and anexcellent color rendering property as in the organic EL element 10 inthe aforementioned first embodiment. Moreover, the organic EL element 30of the embodiment has the MPE structure in which the first lightemitting unit 33A, the second light emitting unit 33B, the third lightemitting unit 33C, and the fourth light emitting unit 33D are stackedone on top of another with each of the first charge generating layer34A, the second charge generating layer 34B, and the third chargegenerating layer 34C sandwiched between the corresponding pair ofadjacent light emitting units. Accordingly, the organic EL element 30can provide the white light while achieving high-luminance lightemission and long-life driving.

The organic EL element 30 of the embodiment can be thus preferably usedin both of a display device and a lighting device.

Fourth Embodiment

FIG. 9 is a cross-sectional view illustrating a schematic configurationof a fourth embodiment of the organic EL element in the presentinvention.

As illustrated in FIG. 9, the organic EL element 40 of the embodimenthas a structure in which multiple light emitting units 43A, 43B, 43C,43D, 43E, 43F each including a light emitting layer made of at least anorganic compound are stacked one on top of another between a firstelectrode 41 and a second electrode 42 with each of charge generatinglayers (CGL) 44A, 44B, 44C, 44D, 44E sandwiched between a correspondingpair of the adjacent light emitting units. The organic EL element 40 isan organic EL element capable of providing white light by causing themultiple light emitting units 43A, 43B, 43C, 43D, 43E, 43F to emitlight.

The organic EL element 40 of the embodiment includes the first lightemitting unit 43A, the second light emitting unit 43B, the third lightemitting unit 43C, the fourth light emitting unit 43D, the fifth lightemitting unit 43E, and the sixth light emitting unit 43F.

The first light emitting unit 43A is a red/green light emitting unit ora red-green light emitting unit. The red/green light emitting unitincludes a light emitting layer formed of a red phosphorescent lightemitting layer which emits red light with one peak wavelength in a redwavelength band and a green phosphorescent light emitting layer whichemits green light with one or two peak wavelengths in a green wavelengthband. Specifically, the red/green light emitting unit is a layer formedby stacking the red phosphorescent light emitting layer and the greenphosphorescent light emitting layer one on top of the other. Thered-green light emitting unit includes alight emitting layer formed of amixed layer of a red phosphorescent material and a green phosphorescentmaterial. Specifically, the red-green light emitting unit is one layer(single layer) containing the red phosphorescent material and the greenphosphorescent material.

The second light emitting unit 43B is a blue light emitting unit. Theblue light emitting unit includes a light emitting layer formed of ablue light emitting layer which emits blue light with one or two peakwavelengths in the blue wavelength band. The blue light emitting layermay be a blue fluorescent light emitting layer containing a bluefluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light provided bythe blue light emitting unit including the blue fluorescent lightemitting layer may include a delayed fluorescence component.

The third light emitting unit 43C is a red/green light emitting unit ora red-green light emitting unit. The red/green light emitting unitincludes a light emitting layer formed of a red phosphorescent lightemitting layer which emits red light with one peak wavelength in a redwavelength band and a green phosphorescent light emitting layer whichemits green light with one or two peak wavelengths in a green wavelengthband. Specifically, the red/green light emitting unit is a layer formedby stacking the red phosphorescent light emitting layer and the greenphosphorescent light emitting layer one on top of the other. Thered-green light emitting unit includes alight emitting layer formed of amixed layer of a red phosphorescent material and a green phosphorescentmaterial. Specifically, the red-green light emitting unit is one layer(single layer) containing the red phosphorescent material and the greenphosphorescent material.

The fourth light emitting unit 43D is a red/green light emitting unit ora red-green light emitting unit. The red/green light emitting unitincludes a light emitting layer formed of a red phosphorescent lightemitting layer which emits red light with one peak wavelength in a redwavelength band and a green phosphorescent light emitting layer whichemits green light with one or two peak wavelengths in a green wavelengthband. Specifically, the red/green light emitting unit is a layer formedby stacking the red phosphorescent light emitting layer and the greenphosphorescent light emitting layer one on top of the other. Thered-green light emitting unit includes alight emitting layer formed of amixed layer of a red phosphorescent material and a green phosphorescentmaterial. Specifically, the red-green light emitting unit is one layer(single layer) containing the red phosphorescent material and the greenphosphorescent material.

The fifth light emitting unit 43E is a blue light emitting unit. Theblue light emitting unit includes a light emitting layer formed of ablue light emitting layer which emits blue light with one or two peakwavelengths in the blue wavelength band. The blue light emitting layermay be a blue fluorescent light emitting layer containing a bluefluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light provided bythe blue light emitting unit including the blue fluorescent lightemitting layer may include a delayed fluorescence component.

The sixth light emitting unit 43F is a red/green light emitting unit ora red-green light emitting unit. The red/green light emitting unitincludes a light emitting layer formed of a red phosphorescent lightemitting layer which emits red light with one peak wavelength in a redwavelength band and a green phosphorescent light emitting layer whichemits green light with one or two peak wavelengths in a green wavelengthband. Specifically, the red/green light emitting unit is a layer formedby stacking the red phosphorescent light emitting layer and the greenphosphorescent light emitting layer one on top of the other. Thered-green light emitting unit includes alight emitting layer formed of amixed layer of a red phosphorescent material and a green phosphorescentmaterial. Specifically, the red-green light emitting unit is one layer(single layer) containing the red phosphorescent material and the greenphosphorescent material.

The first light emitting unit 43A and the second light emitting unit 43Bare stacked one on top of the other with the first charge generatinglayer 44A sandwiched therebetween.

The second light emitting unit 43B and the third light emitting unit 43Care stacked one on top of the other with the second charge generatinglayer 44B sandwiched therebetween.

The third light emitting unit 43C and the fourth light emitting unit 43Dare stacked one on top of the other with the third charge generatinglayer 44C sandwiched therebetween.

The fourth light emitting unit 43D and the fifth light emitting unit 43Eare stacked one on top of the other with the fourth charge generatinglayer 44D sandwiched therebetween.

The fifth light emitting unit 43E and the sixth light emitting unit 43Fare stacked one on top of the other with the fifth charge generatinglayer 44E sandwiched therebetween.

The organic EL element 40 of the embodiment has a structure in which thesecond electrode 42, the sixth light emitting unit 43F, the fifth chargegenerating layer 44E, the fifth light emitting unit 43E, the fourthcharge generating layer 44D, the fourth light emitting unit 43D, thethird charge generating layer 44C, the third light emitting unit 43C,the second charge generating layer 44B, the second light emitting unit43B, the first charge generating layer 44A, the first light emittingunit 43A, and the first electrode 41 are stacked one on top of anotherin this order. Specifically, the organic EL element 40 of the embodimenthas an MPE structure in which the first light emitting unit 43A, thesecond light emitting unit 43B, the third light emitting unit 43C, thefourth light emitting unit 43D, the fifth light emitting unit 43E, andthe sixth light emitting unit 43F are stacked one on top of another witheach of the first charge generating layer 44A, the second chargegenerating layer 44B, the third charge generating layer 44C, the fourthcharge generating layer 44D, and the fifth charge generating layer 44Esandwiched between the corresponding pair of adjacent light emittingunits.

In the organic EL element 40 of the embodiment, the white light producedby light emission of the first light emitting unit 43A, the second lightemitting unit 43B, the third light emitting unit 43C, the fourth lightemitting unit 43D, the fifth light emitting unit 43E, and the sixthlight emitting unit 43F has an emission spectrum continuous over awavelength band of at least 380 nm to 780 nm. Moreover, in the organicEL element 40 of the embodiment, the white light has one or two peakwavelengths in the blue wavelength band of 440 nm to 490 nm in thisemission spectrum. Furthermore, in the organic EL element 40 of theembodiment, the white light has one peak wavelength in the redwavelength band of 590 nm to 640 nm and one or two peak wavelengths inthe green wavelength band of 500 nm to 560 nm in this emission spectrum.

The same electrode as the first electrode 11 in the aforementioned firstembodiment can be used as the first electrode 41.

The same electrode as the second electrode 12 in the aforementionedfirst embodiment can be used as the second electrode 42.

The first light emitting unit 43A is formed of a first electrontransport layer 45A, a first light emitting layer 46A, and a first holetransport layer 47A. The second light emitting unit 43B is formed of asecond electron transport layer 45B, a second light emitting layer 46B,and a second hole transport layer 47B. The third light emitting unit 43Cis formed of a third electron transport layer 45C, a third lightemitting layer 46C, and a third hole transport layer 47C. The fourthlight emitting unit 43D is formed of a fourth electron transport layer45D, a fourth light emitting layer 46D, and a fourth hole transportlayer 47D. The fifth light emitting unit 43E is formed of a fifthelectron transport layer 45E, a fifth light emitting layer 46E, and afifth hole transport layer 47E. The sixth light emitting unit 43F isformed of a sixth electron transport layer 45F, a sixth light emittinglayer 46F, and a sixth hole transport layer 47F.

The first light emitting unit 43A, the second light emitting unit 43B,the third light emitting unit 43C, the fourth light emitting unit 43D,the fifth light emitting unit 43E, and the sixth light emitting unit 43Fmay employ any of various structures similar to those ofconventionally-known organic EL elements and may have any laminatedstructure as long as they include light emitting layers made of at leastan organic compound. For example, each of the first light emitting unit43A, the second light emitting unit 43B, the third light emitting unit43C, the fourth light emitting unit 43D, the fifth light emitting unit43E, and the sixth light emitting unit 43F may be configured such thatan electron injection layer, a hole blocking layer, and the like arearranged on the first electrode 41 side of the light emitting layer anda hole injection layer, an electron blocking layer, and the like arearranged on the second electrode 42 side of the light emitting layer.

The electron transport layers have the same configuration as that of theelectron transport layers in the aforementioned first embodiment.

The hole transport layers have the same configuration as that of thehole transport layers in the aforementioned first embodiment.

When the first light emitting unit 43A is the red/green light emittingunit, the light emitting layer included in the first light emitting unit43A is formed of a red phosphorescent light emitting layer and a greenphosphorescent light emitting layer. The red phosphorescent lightemitting layer and the green phosphorescent light emitting layer eachcontain a host material which is a main component and a guest materialwhich is a minor component as the organic compound. When the first lightemitting unit 43A is the red-green light emitting unit, the lightemitting layer included in the first light emitting unit 43A is formedof a mixed layer of a red phosphorescent material and a greenphosphorescent material. The mixed layer of the red phosphorescentmaterial and the green phosphorescent material contains a host materialwhich is a main component and a guest material which is a minorcomponent as the organic compound. The red phosphorescent material andthe green phosphorescent material correspond to the guest material outof these materials. In either case, emission of the red light and thegreen light is attributable particularly to the properties of the guestmaterial. Moreover, when the light emitting layer is formed of the mixedlayer of the red phosphorescent material and the green phosphorescentmaterial, it is important that light is efficiently emitted from bothlight emitting materials. To achieve this, it is effective to set theproportion of the red phosphorescent material lower than the proportionof the green phosphorescent material. This is due to the followingreason. Since the energy level of the red phosphorescent material islower than the energy level of the green phosphorescent material, energytransfer to the red phosphorescent material is more likely to occur.Accordingly, setting the proportion of the red phosphorescent materiallower than the proportion of the green phosphorescent material allowsboth of the red phosphorescent material and the green phosphorescentmaterial to efficiently emit light.

As the host material of the light emitting layer included in the firstlight emitting unit 43A, the same material as the host material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

As the guest material of the light emitting layer included in the firstlight emitting unit 43A, the same material as the guest material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

The blue light emitting layer included in the second light emitting unit43B is formed of a blue fluorescent light emitting layer containing ablue fluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light emitting layercontains a host material which is a main component and a guest materialwhich is a minor component as the organic compound. The blue fluorescentmaterial or the blue phosphorescent material corresponds to the guestmaterial out of these materials. In either case, emission of the bluelight is attributable particularly to the properties of the guestmaterial.

As the host material of the blue light emitting layer included in thesecond light emitting unit 43B, the same material as the host materialof the blue light emitting layers in the aforementioned first embodimentcan be used.

As the guest material of the blue light emitting layer included in thesecond light emitting unit 43B, the same material as the guest materialof the blue light emitting layers in the aforementioned first embodimentcan be used.

When the third light emitting unit 43C is the red/green light emittingunit, the light emitting layer included in the third light emitting unit43C is formed of a red phosphorescent light emitting layer and a greenphosphorescent light emitting layer. The red phosphorescent lightemitting layer and the green phosphorescent light emitting layer eachcontain a host material which is a main component and a guest materialwhich is a minor component as the organic compound. When the third lightemitting unit 43C is the red-green light emitting unit, the lightemitting layer included in the third light emitting unit 43C is formedof a mixed layer of a red phosphorescent material and a greenphosphorescent material. The mixed layer of the red phosphorescentmaterial and the green phosphorescent material contains a host materialwhich is a main component and a guest material which is a minorcomponent as the organic compound. The red phosphorescent material andthe green phosphorescent material correspond to the guest material outof these materials. In either case, emission of the red light and thegreen light is attributable particularly to the properties of the guestmaterial. Moreover, when the light emitting layer is formed of the mixedlayer of the red phosphorescent material and the green phosphorescentmaterial, it is important that light is efficiently emitted from bothlight emitting materials. To achieve this, it is effective to set theproportion of the red phosphorescent material lower than the proportionof the green phosphorescent material. This is due to the followingreason. Since the energy level of the red phosphorescent material islower than the energy level of the green phosphorescent material, energytransfer to the red phosphorescent material is more likely to occur.Accordingly, setting the proportion of the red phosphorescent materiallower than the proportion of the green phosphorescent material allowsboth of the red phosphorescent material and the green phosphorescentmaterial to efficiently emit light.

As the host material of the light emitting layer included in the thirdlight emitting unit 43C, the same material as the host material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

As the guest material of the light emitting layer included in the thirdlight emitting unit 43C, the same material as the guest material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

When the fourth light emitting unit 43D is the red/green light emittingunit, the light emitting layer included in the fourth light emittingunit 43D is formed of a red phosphorescent light emitting layer and agreen phosphorescent light emitting layer. The red phosphorescent lightemitting layer and the green phosphorescent light emitting layer eachcontain a host material which is a main component and a guest materialwhich is a minor component as the organic compound. When the fourthlight emitting unit 43D is the red-green light emitting unit, the lightemitting layer included in the fourth light emitting unit 43D is formedof a mixed layer of a red phosphorescent material and a greenphosphorescent material. The mixed layer of the red phosphorescentmaterial and the green phosphorescent material contains a host materialwhich is a main component and a guest material which is a minorcomponent as the organic compound. The red phosphorescent material andthe green phosphorescent material correspond to the guest material outof these materials. In either case, emission of the red light and thegreen light is attributable particularly to the properties of the guestmaterial. Moreover, when the light emitting layer is formed of the mixedlayer of the red phosphorescent material and the green phosphorescentmaterial, it is important that light is efficiently emitted from bothlight emitting materials. To achieve this, it is effective to set theproportion of the red phosphorescent material lower than the proportionof the green phosphorescent material. This is due to the followingreason. Since the energy level of the red phosphorescent material islower than the energy level of the green phosphorescent material, energytransfer to the red phosphorescent material is more likely to occur.Accordingly, setting the proportion of the red phosphorescent materiallower than the proportion of the green phosphorescent material allowsboth of the red phosphorescent material and the green phosphorescentmaterial to efficiently emit light.

As the host material of the light emitting layer included in the fourthlight emitting unit 43D, the same material as the host material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

As the guest material of the light emitting layer included in the fourthlight emitting unit 43D, the same material as the guest material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

The blue light emitting layer included in the fifth light emitting unit43E is formed of a blue fluorescent light emitting layer containing ablue fluorescent material or a blue phosphorescent light emitting layercontaining a blue phosphorescent material. The blue light emitting layercontains a host material which is a main component and a guest materialwhich is a minor component as the organic compound. The blue fluorescentmaterial or the blue phosphorescent material corresponds to the guestmaterial out of these materials. In either case, emission of the bluelight is attributable particularly to the properties of the guestmaterial.

As the host material of the blue light emitting layer included in thefifth light emitting unit 43E, the same material as the host material ofthe blue light emitting layers in the aforementioned first embodimentcan be used.

As the guest material of the blue light emitting layer included in thefifth light emitting unit 43E, the same material as the guest materialof the blue light emitting layers in the aforementioned first embodimentcan be used.

When the sixth light emitting unit 43F is the red/green light emittingunit, the light emitting layer included in the sixth light emitting unit43F is formed of a red phosphorescent light emitting layer and a greenphosphorescent light emitting layer. The red phosphorescent lightemitting layer and the green phosphorescent light emitting layer eachcontain a host material which is a main component and a guest materialwhich is a minor component as the organic compound. When the sixth lightemitting unit 43F is the red-green light emitting unit, the lightemitting layer included in the sixth light emitting unit 43F is formedof a mixed layer of a red phosphorescent material and a greenphosphorescent material. The mixed layer of the red phosphorescentmaterial and the green phosphorescent material contains a host materialwhich is a main component and a guest material which is a minorcomponent as the organic compound. The red phosphorescent material andthe green phosphorescent material correspond to the guest material outof these materials. In either case, emission of the red light and thegreen light is attributable particularly to the properties of the guestmaterial. Moreover, when the light emitting layer is formed of the mixedlayer of the red phosphorescent material and the green phosphorescentmaterial, it is important that light is efficiently emitted from bothlight emitting materials. To achieve this, it is effective to set theproportion of the red phosphorescent material lower than the proportionof the green phosphorescent material. This is due to the followingreason. Since the energy level of the red phosphorescent material islower than the energy level of the green phosphorescent material, energytransfer to the red phosphorescent material is more likely to occur.Accordingly, setting the proportion of the red phosphorescent materiallower than the proportion of the green phosphorescent material allowsboth of the red phosphorescent material and the green phosphorescentmaterial to efficiently emit light.

As the host material of the light emitting layer included in the sixthlight emitting unit 43F, the same material as the host material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

As the guest material of the light emitting layer included in the sixthlight emitting unit 43F, the same material as the guest material of thelight emitting layer included in the first light emitting unit 13A inthe aforementioned first embodiment can be used.

For example, a vacuum deposition method, a spin coating method, or thelike can be used as a film forming method of the layers forming thefirst light emitting unit 43A, the second light emitting unit 43B, thethird light emitting unit 43C, the fourth light emitting unit 43D, thefifth light emitting unit 43E, and the sixth light emitting unit 43F.

The first charge generating layer 44A, the second charge generatinglayer 44B, the third charge generating layer 44C, the fourth chargegenerating layer 44D, and the fifth charge generating layer 44E are eachformed of an electrically insulating layer made of an electron acceptingmaterial and an electron donating material. The specific resistance ofthe electrically insulating layer is preferably 1.0×10²Ω·cm or more,more preferably 1.0×10⁵Ω·cm or more.

Alternatively, the first charge generating layer 44A, the second chargegenerating layer 44B, the third charge generating layer 44C, the fourthcharge generating layer 44D, and the fifth charge generating layer 44Emay each be configured such that the charge generating layer is formedof a mixed layer of different materials and one component of the mixedlayer forms a charge transfer complex by redox. In this case, whenvoltage is applied between the first electrode 41 and the secondelectrode 42, charges in the charge transfer complex move to the firstelectrode 41 side and the second electrode 42 side. In the organic ELelement 40, holes are thereby injected into the fifth light emittingunit 43E located on the first electrode 41 side of the fifth chargegenerating layer 44E, the fourth light emitting unit 43D located on thefirst electrode 41 side of the fourth charge generating layer 44D, thethird light emitting unit 43C located on the first electrode 41 side ofthe third charge generating layer 44C, the second light emitting unit43B located on the first electrode 41 side of the second chargegenerating layer 44B, and the first light emitting unit 43A located onthe first electrode 41 side of the first charge generating layer 44A.Moreover, in the organic EL element 40, electrons are injected into thesixth light emitting unit 43F located on the second electrode 42 side ofthe fifth charge generating layer 44E, the fifth light emitting unit 43Elocated on the second electrode 42 side of the fourth charge generatinglayer 44D, the fourth light emitting unit 43D located on the secondelectrode 42 side of the third charge generating layer 44C, the thirdlight emitting unit 43C located on the second electrode 42 side of thesecond charge generating layer 44B, and the second light emitting unit43B located on the second electrode 42 side of the first chargegenerating layer 44A. Light can be thereby simultaneously emitted fromthe first light emitting unit 43A, the second light emitting unit 43B,the third light emitting unit 43C, the fourth light emitting unit 43D,the fifth light emitting unit 43E, and the sixth light emitting unit 43Fwith the same current amount. Accordingly, a current efficiency and anexternal quantum efficiency proportionate to the sum of luminousefficiencies of the first light emitting unit 43A, the second lightemitting unit 43B, the third light emitting unit 43C, the fourth lightemitting unit 43D, the fifth light emitting unit 43E, and the sixthlight emitting unit 43F can be obtained.

Alternatively, the first charge generating layer 44A, the second chargegenerating layer 44B, the third charge generating layer 44C, the fourthcharge generating layer 44D, and the fifth charge generating layer 44Emay each be a laminate of an electron accepting material and an electrondonating material. In this case, when voltage is applied between thefirst electrode 41 and the second electrode 42, in an interface betweenthe electron accepting material and the electron donating material,charges generated by reaction involving electron transfer between theseelectron accepting material and electron donating material move to thefirst electrode 41 side and the second electrode 42 side. In the organicEL element 40, holes are thereby injected into the fifth light emittingunit 43E located on the first electrode 41 side of the fifth chargegenerating layer 44E, the fourth light emitting unit 43D located on thefirst electrode 41 side of the fourth charge generating layer 44D, thethird light emitting unit 43C located on the first electrode 41 side ofthe third charge generating layer 44C, the second light emitting unit43B located on the first electrode 41 side of the second chargegenerating layer 44B, and the first light emitting unit 43A located onthe first electrode 41 side of the first charge generating layer 44A.Moreover, in the organic EL element 40, electrons are injected into thesixth light emitting unit 43F located on the second electrode 42 side ofthe fifth charge generating layer 44E, the fifth light emitting unit 43Elocated on the second electrode 42 side of the fourth charge generatinglayer 44D, the third fourth light emitting unit 43D located on thesecond electrode 42 side of the third charge generating layer 44C, thethird light emitting unit 43C located on the second electrode 42 side ofthe second charge generating layer 44B, and the second light emittingunit 43B located on the second electrode 42 side of the first chargegenerating layer 44A. Light can be thereby simultaneously emitted fromthe first light emitting unit 43A, the second light emitting unit 43B,the third light emitting unit 43C, the fourth light emitting unit 43D,the fifth light emitting unit 43E, and the sixth light emitting unit 43Fwith the same current amount. Accordingly, a current efficiency and anexternal quantum efficiency proportionate to the sum of luminousefficiencies of the first light emitting unit 43A, the second lightemitting unit 43B, the third light emitting unit 43C, the fourth lightemitting unit 43D, the fifth light emitting unit 43E, and the sixthlight emitting unit 43F can be obtained.

As materials forming the first charge generating layer 44A, the secondcharge generating layer 44B, the third charge generating layer 44C, thefourth charge generating layer 44D, and the fifth charge generatinglayer 44E, the same materials as the materials forming the first chargegenerating layer 14A and the second charge generating layer 14B in theaforementioned first embodiment can be used.

The organic EL element 40 having the structure described above canprovide white light by causing the first light emitting unit 43A, thesecond light emitting unit 43B, the third light emitting unit 43C, thefourth light emitting unit 43D, the fifth light emitting unit 43E, andthe sixth light emitting unit 43F to emit light.

Moreover, the organic EL element 40 of the embodiment can provide whitelight with high color temperature, high luminous efficiency, and anexcellent color rendering property as in the organic EL element 10 inthe aforementioned first embodiment. Moreover, the organic EL element 40of the embodiment has the MPE structure in which the first lightemitting unit 43A, the second light emitting unit 43B, the third lightemitting unit 43C, the fourth light emitting unit 43D, the fifth lightemitting unit 43E, and the sixth light emitting unit 43F are stacked oneon top of another with each of the first charge generating layer 44A,the second charge generating layer 44B, the third charge generatinglayer 44C, the fourth charge generating layer 44D, and the fifth chargegenerating layer 44E sandwiched between the corresponding pair ofadjacent light emitting units. Accordingly, the organic EL element 40can provide the white light while achieving high-luminance lightemission and long-life driving.

The organic EL element 40 of the embodiment can be thus preferably usedin both of a display device and a lighting device.

Fifth Embodiment

FIG. 10 is a cross-sectional view illustrating a schematic configurationof a fifth embodiment of the organic EL element in the presentinvention.

As illustrated in FIG. 10, the organic EL element 50 of the embodimenthas a structure in which multiple organic EL elements 10 in theaforementioned first embodiment are provided side by side on atransparent substrate 58. In this configuration, the organic EL elements10 are sectioned based on the respective second electrodes 12 providedon the transparent substrate 58 at certain intervals.

Each of the organic EL elements 10 forms a light emitting portion of theorganic EL element 50 and three different color filters 59A, 59B, 59C ofred, green, and blue are arranged in turn at positions corresponding tothe respective light emitting portions with the transparent substrate 58therebetween.

White light provided by each organic EL element 10 is converted to redlight, green light, or blue light by one of the three different colorfilters 59A, 59B, 59C of red, green, and blue (red color filter 59A,green color filter 59B, or blue color filter 59C) and is emitted to theoutside.

In the organic EL element 50 of the embodiment, it is thus possible toextract red light, green light, and blue light with high color puritybased on white light with high color temperature, high luminousefficiency, and an excellent color rendering property.

An arrangement in which the red color filter 59A, the green color filter59B, and the blue color filter 59C are arranged in turn forms an RGBarrangement. The RGB arrangement may be any arrangement selected fromthe group consisting of a stripe arrangement in which R, G, and B arearranged linearly, a mosaic arrangement in which R, G, and B arearranged diagonally, a delta arrangement in which R, G, and B arearranged in a triangular shape, and a pentile arrangement in which RGand GB are arranged alternately.

Image display with high resolution and natural color can be therebyachieved in a display device.

The organic EL element 50 of the embodiment can be thus preferably usedin a display device.

Note that the organic EL element 50 of the embodiment is not necessarilylimited to the aforementioned configuration and can be changed asappropriate. In the organic EL element 50 of the embodiment, the organicEL element 20 of the second embodiment, the organic EL element 30 of thethird embodiment, or the organic EL element 40 of the fourth embodimentdescribed above can be used instead of the organic EL element 10.

Moreover, the organic EL element 50 of the embodiment may have such astructure that the three different color filters of red, green, and blueare provided between the transparent substrate 58 and the secondelectrodes 12.

Sixth Embodiment

FIG. 11 is a cross-sectional view illustrating a schematic configurationof a sixth embodiment of the organic EL element in the presentinvention.

As illustrated in FIG. 11, the organic EL element 60 of the embodimenthas a structure in which multiple organic EL elements 10 in theaforementioned first embodiment are provided side by side on atransparent substrate 68. In this configuration, the organic EL elements10 are sectioned based on the respective second electrodes 12 providedon the transparent substrate 68 at certain intervals.

Each of the organic EL elements 10 forms a light emitting portion of theorganic EL element 60 and three different color filters 69A, 69B, 69C ofred, green, and blue and a no-color-filter portion are arranged in turnat positions corresponding to the respective light emitting portionswith the transparent substrate 68 therebetween.

White light provided by each organic EL element 10 is converted to redlight, green light, or blue light by one of the three different colorfilters 69A, 69B, 69C of red, green, and blue (red color filter 69A,green color filter 69B, or blue color filter 69C) and is emitted to theoutside.

In the organic EL element 60 of the embodiment, it is thus possible toextract red light, green light, blue light with high color purity basedon original white light with high color temperature, high luminousefficiency, and an excellent color rendering property.

Moreover, in the no-color-filter portion (portion where none of the redcolor filter 69A, green color filter 69B, and blue color filter 69C isprovided on the transparent substrate 68 illustrated in FIG. 11), thewhite light provided by the organic EL element 10 is emitted to theoutside as it is.

An arrangement in which the red color filter 69A, the green color filter69B, and the blue color filter 69C are arranged in turn and theno-color-filter portion form an RGBW arrangement. The RGBW arrangementmay be any arrangement selected from the group consisting of a stripearrangement in which R, G, B, and W are arranged linearly, a mosaicarrangement in which R, G, B, and Ware arranged diagonally, a deltaarrangement in which R, G, B, and Ware arranged in a triangular shape,and a pentile arrangement in which RG and BW are alternately arranged.

When white is displayed on a display, in the RGB method described in[0136], light of a white backlight is absorbed by the color filters ofthe respective colors upon passing the color filters and the luminanceof the light is thereby reduced. Accordingly, the light amount of thebacklight needs to be increased and this leads to an increase in thepower consumption of the display.

Meanwhile, in the RGBW method, there is no color filter in the lightemitting portion of W. Accordingly, when white is displayed, the lightemission from the white backlight can be effectively used as it is.Hence, there is no decrease in luminance and an operation can beachieved with low power consumption.

Thus, low power consumption and image display with high resolution andnatural color can be both achieved in a display device.

The organic EL element 60 of the embodiment can be thus preferably usedin a display device.

Note that the organic EL element 60 of the embodiment is not necessarilylimited to the aforementioned configuration and can be changed asappropriate. In the organic EL element 60 of the embodiment, the organicEL element 20 of the second embodiment, the organic EL element 30 of thethird embodiment, or the organic EL element 40 of the fourth embodimentdescribed above can be used instead of the organic EL element 10.

Moreover, the organic EL element 60 of the embodiment may have such astructure that the three different color filters of red, green, and blueare provided between the transparent substrate 68 and the secondelectrodes 12.

[Lighting Device]

An embodiment of the lighting device in the present invention isdescribed.

FIG. 12 is a cross-sectional view illustrating a configuration of theembodiment of the lighting device in the present invention. Although anexample of the lighting device to which the present invention is appliedis described herein, the lighting device of the present invention is notnecessarily limited to such a configuration and various changes can bemade as appropriate.

The lighting device 100 of the embodiment includes, for example, any oneof the organic EL elements 10, 20, 30, 40, 50 as a light source.

As illustrated in FIG. 12, in the lighting device 100 of the embodiment,multiple anode terminal electrodes 111 and cathode terminal electrodes(illustration omitted) are formed at sides or vertices of a periphery ofa glass substrate 110 so that the organic EL element 10, 20, 30, 40, 50can uniformly emit light. Note that the entire surfaces of the anodeterminal electrodes 111 and the entire surfaces of the cathode terminalelectrodes are covered with solder (underlying solder) to reduce wiringresistance. Moreover, the anode terminal electrodes 111 and the cathodeterminal electrodes uniformly supply an electric current to the organicEL element 10, 20, 30, 40, 50 from the sides or vertices of theperiphery of the glass substrate 110. For example, in order to uniformlysupply an electric current to the organic EL element 10, 20, 30, 40, 50formed in a quadrilateral shape, the lighting device 100 includes theanode terminal electrodes 111 on the sides and the cathode terminalelectrodes at the vertices. Alternatively, for example, the lightingdevice 100 includes the anode terminal electrodes 111 on peripheries ofL-shaped portions each including a vertex and extending over two sidesand the cathode terminal electrodes in center portions of the respectivesides.

Moreover, a sealing substrate 113 is arranged on the glass substrate 110to cover the organic EL element 10, 20, 30, 40, 50 to prevent degradingof the performance of the organic EL element 10, 20, 30, 40, 50 due tooxygen, water, and the like. The sealing substrate 113 is provided onthe glass substrate 110 with a peripheral sealing member 114therebetween. A small gap 115 is provided between the sealing substrate113 and the organic EL element 10, 20, 30, 40, 50. This gap 115 isfilled with a hygroscopic agent. The gap 115 may be filled with, forexample, an inert gas such as nitrogen, silicone oil, or the likeinstead of the hygroscopic agent. Moreover, the gap 115 may be filledwith a gel resin in which the hygroscopic agent is dispersed.

Note that, although the glass substrate 110 is used as a base substratefor forming the element in the embodiment, a substrate made of amaterial such as plastic, metal, or ceramic may also be used. Moreover,in the embodiment, a glass substrate, a plastic substrate, or the likecan be used as the sealing substrate 113. When plastic substrates areused as the base substrate and the sealing substrate, the lightingdevice 100 of the embodiment is flexible.

Moreover, a UV curable resin or a thermal setting resin with low oxygenpermeability and low water permeability, a laser glass frit, or the likecan be used for the sealing member 114.

The lighting device of the embodiment may have a configuration includingan optical film for improving the luminous efficiency, on the lightextraction surface side of the organic EL element 10, 20, 30, 40, 50 inthe aforementioned embodiment.

The optical film used in the lighting device of the embodiment isprovided to improve the luminous efficiency while maintaining the colorrendering property.

An organic EL element emits light in a light emitting layer with ahigher refractive index (refractive index of about 1.6 to 2.1) than airand it is generally said that only about 15% to 20% of light emittedfrom the light emitting layer can be extracted. This is because lightincident on an interface at an angle equal to or greater than a criticalangle is totally reflected and cannot be extracted to the outside of theelement. Specifically, light is totally reflected between a transparentsubstrate and a transparent electrode or the light emitting layer to beguided through the transparent electrode or the light emitting layer andresultantly escapes in directions toward side surfaces of the element.

As a method for improving the extraction efficiency of the light, thereare, for example, the following methods: a method of making a surface ofthe transparent substrate rough to prevent total reflection on aninterface between the transparent substrate and air (see, for example,“U.S. Pat. No. 4,774,435”); a method of providing the substrate with alight condensing property to improve the efficiency (see, for example,“Japanese Patent Application Publication No. Sho 63-314795”); a methodof forming reflection surfaces on the side surfaces of the element andthe like (see, for example, “Japanese Patent Application Publication No.Hei 1-220394”); a method of introducing a flat layer with anintermediate refractive index between the substrate and the lightemitting body to form a reflection prevention film (see, for example,“Japanese Patent Application Publication No. Sho 62-172691”); a methodof introducing a flat layer with a lower refractive index than thesubstrate, between the substrate and the light emitting body (see, forexample, “Japanese Patent Application Publication No. 2001-202827”); amethod of forming a diffraction grading between any two of thesubstrate, the transparent electrode layer, and the light emitting layer(including between the substrate and the outside) (see, for example,“Japanese Patent Application Publication No. Hei 11-283751”); and thelike.

Note that, in order to improve the aforementioned color renderingproperty, the lighting device 100 may have a structure in which amicrolens array or the like is further provided on a surface of theaforementioned optical film or may be combined with a light condensingsheet. This allows the light to be condensed in a specific direction,for example, a direction frontward of the element light emittingsurface, thereby improving the luminance in the specific direction.Furthermore, a light diffusion film may be used together with the lightcondensing sheet to control a light emission angle from the organic ELelement. For example, a light diffusion film (LIGHT-UP) manufactured byKimoto Co., Ltd. or the like can be used as the light diffusion film.

Note that the present invention is not necessarily limited to theaforementioned embodiment and various changes can be made within a scopenot departing from the spirit of the present invention.

Specifically, in the present invention, any of the organic EL elements10, 20, 30, 40, 50 capable of providing the aforementioned white lightcan be preferably used as the light source of the lighting device 100which is, for example, a general lighting device. Meanwhile, in thepresent invention, the organic EL elements 10, 20, 30, 40, 50 are notlimited for use as the light source of the lighting device 100 and maybe used in various applications such as, for example, a backlight of aliquid crystal display.

[Display Device]

An embodiment of the display device in the present invention isdescribed.

FIG. 13 is a cross-sectional view illustrating a configuration of theembodiment of the display device in the present invention. In FIG. 13,the same constitutional elements as those in the first embodiment of theorganic EL element in the present invention illustrated in FIG. 1 andthe fifth embodiment of the organic EL element in the present inventionillustrated in FIG. 10 are denoted by the same reference numerals anddescription thereof is omitted. Moreover, although an example of thedisplay device to which the present invention is applied is describedherein, the display device of the present invention is not necessarilylimited to such a configuration and changes can be made as appropriate.

The display device 200 of the embodiment includes, for example, theorganic EL element 10 as the light source, the organic EL element 10having a light emitting layer 16 including a first light emittingportion 16A, a second light emitting portion 16B, and a third lightemitting portion 16C as described above.

The display device 200 of the embodiment is a top emission type and isan active matrix type.

As illustrated in FIG. 13, the display device 200 of the embodimentincludes a TFT substrate 300, an organic EL element 400, a color filter500, and a sealing substrate 600. In the display device 200 of theembodiment, the TFT substrate 300, the organic EL element 400, the colorfilter 500, and the sealing substrate 600 are stacked one on top ofanother in this order to form a laminated structure.

The TFT substrate 300 includes a base substrate 310, TFT elements 320which are provided on one surface 310 a of the base substrate 310, andan insulating layer 330 which is a planarization film layer (protectionlayer) provided on the one surface 310 a of the base substrate 310 tocover the TFT elements 320.

A glass substrate, a flexible substrate made of plastic, and the likecan be given as examples of the base substrate 310.

The TFT elements 320 each include a source electrode 321, a drainelectrode 322, a gate electrode 323, a gate insulating layer 324 formedon the gate electrode 323, and a channel region provided on the gateinsulating layer 324 and being in contact with the source electrode 321and the drain electrode 322.

The organic EL element 400 has the same configuration as the organic ELelement 10.

The light emitting layer 16 in the organic EL element 400 includes thefirst light emitting portion 16A which emits red light, the second lightemitting portion 16B which emits green light, and the third lightemitting portion 16C which emits blue light.

First partition walls (banks) 410 and second partition walls (ribs) 420stacked thereon are provided between the first light emitting portion16A and the second light emitting portion 16B, between the second lightemitting portion 16B and the third light emitting portion 16C, andbetween the third light emitting portion 16C and the first lightemitting portion 16A.

The first partition walls 410 are provided on the insulating layer 330.The first partition walls 410 have a shape tapered in a direction awayfrom the insulating layer 330. The width of the first partition walls410 gradually becomes smaller as the distance from the insulating layer330 increases.

The second partition walls 420 are provided on the first partition walls410. The second partition walls 420 have a shape reverse-tapered in adirection away from the first partition walls 410. The width of thesecond partition walls 420 gradually becomes greater as the distancefrom the first partition walls 410 increases.

The first partition walls 410 and the second partition walls 420 aremade of an insulating material. A fluorine-containing resin can be givenas an example of the material forming the first partition walls 410 andthe second partition walls 420. Vinylidene fluoride, vinyl fluoride,trifluoroethylene, copolymers of these, and the like can be given asexamples of a fluorine compound contained in the fluorine-containingresin. A phenol novolac resin, a polyvinyl phenol resin, an acrylicresin, a methacrylic resin, and combination of these can be given asexamples of a resin contained in the fluorine-containing resin.

The first light emitting portion 16A, the second light emitting portion16B, and the third light emitting portion 16C are provided on a secondelectrode 13 formed on the insulating layer 330 of the TFT elements 320,with a hole transport layer 15 provided between the insulating layer 330and the light emitting portions 16A, 16B, 16C.

The second electrode 13 is connected to the drain electrodes 322 of theTFT elements 320.

The color filter 500 is provided on a first electrode 12 of the organicEL element 400.

The color filter 500 includes a first color filter 510 corresponding tothe first light emitting portion 16A, a second color filter 520corresponding to the second light emitting portion 16B, and a thirdcolor filter 530 corresponding to the third light emitting portion 16C.

The first color filter 510 is a red color filter and is arranged to facethe first light emitting portion 16A.

The second color filter 520 is a green color filter and is arranged toface the second light emitting portion 16B.

The third color filter 530 is a blue color filter and is arranged toface the third light emitting portion 16C.

A glass substrate, a flexible substrate made of plastic, and the likecan be given as examples of the sealing substrate 600. When plastic isused for the base substrate 310 and the sealing substrate 600, thedisplay device 200 of the embodiment is flexible.

Note that, as illustrated in FIG. 13, although the example in which thelight emitting layer 16 of the organic EL element 400 includes the firstlight emitting portion 16A which emits red light, the second lightemitting portion 16B which emits green light, and the third lightemitting portion 16C which emits blue light are described in theembodiment, the embodiment is not limited to this. The light emittinglayer 16 may include the first light emitting portion 16A which emitsred light, the second light emitting portion 16B which emits greenlight, the third light emitting portion 16C which emits blue light, anda fourth light emitting portion 16D which emits white light. Note thatnone of the color filters are disposed at a position corresponding tothe fourth light emitting portion 16D.

The display device 200 of the embodiment can provide white light withhigh color temperature, high luminous efficiency, and an excellent colorrendering property. Moreover, since the display device 200 of theembodiment includes the organic EL element 50 in the fifth embodiment,the display device 200 can provide white light whose correlated colortemperature is 3300 or more, average color rendering index (Ra) is 70 ormore, and R6 and R12 among the special color rendering indices (Ri) are60 or more and 30 or more, respectively.

Note that the present invention is not necessarily limited to theaforementioned embodiment and various changes can be made within a scopenot departing from the spirit of the present invention. In the displaydevice 200 of the embodiment, the organic EL element 60 in theaforementioned sixth embodiment can be used instead of the organic ELelement 50.

EXAMPLES

Effects of the present invention are made clearer below by usingExamples.

Note that the present invention is not limited to following Examples andchanges can be made as appropriate within a scope not departing from thespirit of the invention.

Example 1

“Manufacturing of Organic EL Element”

In Example 1, an organic EL element having an element structureillustrated in FIG. 14 was manufactured.

Specifically, first, there was prepared a soda-lime glass substrate witha thickness of 0.7 mm on which an ITO film with a thickness of 100 nm, awidth of 2 mm, and a sheet resistance of about 20Ω/□ was formed.

Then, the substrate was subjected to ultrasonic cleaning by usingneutral detergent, ion-exchanged water, acetone, and isopropyl alcoholfor 5 minutes for each cleaner and then subjected to spin drying andUV/O₃ treatment.

Next, vapor deposition crucibles (made of tantalum or alumina) in avacuum deposition apparatus were filled respectively with materials usedto form layers illustrated in FIG. 14. Then, the substrate was set inthe vacuum deposition apparatus, electric power was supplied to thevapor deposition crucibles to heat them in a reduced pressure atmospherewith a degree of vacuum of 1×10⁻⁴ Pa or less, and each of the layers wasvapor-deposited to a predetermined film thickness at a deposition rateof 0.1 nm per second. Moreover, each of the layers made of two or morematerials such as the light emitting layers was formed by supplyingpower to the corresponding vapor deposition crucibles and performingco-deposition such that the layer was formed to have a predetermined mixratio.

Moreover, the first electrode was vapor-deposited to a predeterminedfilm thickness at a deposition rate of 1 nm per second.

“Evaluation of Organic EL Element”

The organic EL element of Example 1 manufactured as described above wasconnected to a power supply (KEITHLEY 2425) and power with a constantcurrent of 3 mA/cm² was supplied to the organic EL element of Example 1to cause it to emit light. An emission spectrum of light emitted fromthe organic EL element in the frontward direction in this case wasmeasured by using a multichannel analyzer (trade name: PMA-11,manufactured by Hamamatsu Photonics K. K.).

Then, the emitted light color was evaluated based on the measurementresult by using chromaticity coordinates in the CIE color system.Moreover, the emitted light color was classified into one of lightsource colors specified in “JIS Z 9112” based on the chromaticitycoordinates. Furthermore, the deviation duv from a blackbody locus wasderived based on the specifications of “JIS Z 8725.” Moreover, theaverage color rendering index (Ra) of the emitted light color wasderived by using the method specified in “JIS Z 8726.” The results (nofilm) of these evaluations are collectively illustrated in FIG. 15.

Example 2

An organic EL element of Example 2 having an element structureillustrated in FIG. 16 was manufactured by using the same manufacturingmethod as that of Example 1.

Then, the organic EL element of Example 2 was evaluated in the samemethods as those in Example 1. The evaluation results (no film) areillustrated in FIG. 17.

As illustrated in FIGS. 15 and 17, the organic EL elements of Examples 1and 2 both provided the white light with high color temperature, highluminous efficiency, and an excellent color rendering property.Accordingly, it was found that lighting devices and display devicesincluding such an organic EL element can be lighting devices and displaydevices with high color temperature, high luminous efficiency, and anexcellent color rendering property.

Example 3

An optical film was attached to the light extraction surface (secondelectrode) side of the organic EL element of the aforementioned Example1 to manufacture a lighting device of Example 3.

Then, the lighting device of Example 3 was evaluated in the same methodsas those in Example 1. The evaluation results (with film) areillustrated in FIG. 15.

Example 4

An optical film was attached to the light extraction surface (secondelectrode) side of the organic EL element of the aforementioned Example2 to manufacture a lighting device of Example 4.

Then, the lighting device of Example 4 was evaluated in the same methodsas those in Example 1. The evaluation results (with film) areillustrated in FIG. 17.

As illustrated in FIGS. 15 and 17, it was found that, in the lightingdevices of Examples 3 and 4, attaching the optical film to the lightextraction surface (second electrode) side of the organic EL elementchanged the shape of the emission spectrum from that in the case whereno optical film was attached (illustrated by broken lines in FIGS. 15and 17). Particularly, it was found that the light emission intensitiesof the two peak wavelengths appearing in the green wavelength band andthe red wavelength band were increased as compared with those obtainedwithout the films.

Thus, in the lighting devices of Examples 3 and 4, the luminousefficiency was greatly improved while maintaining the high colortemperature and the excellent color rendering property of the organic ELelements in Examples 1 and 2. The luminous efficiency was improved toabout 1.4 times the luminous efficiency of the organic EL element ofExample 1 while maintaining high color temperature of 3300 K or more andan excellent color rendering property of Ra of 80 or more, R6 of 60 ormore, and R12 of 30 or more.

INDUSTRIAL APPLICABILITY

One aspect described above can provide an organic electroluminescentelement which can provide white light with high color temperature, highluminous efficiency, and an excellent color rendering property and isthus suitable for both of a display device and a lighting device andalso provide a display device and a lighting device including thisorganic electroluminescent element.

DESCRIPTION OF REFERENCE NUMERALS

-   10, 20, 30, 40, 50, 60 organic EL element-   11, 21, 31, 41, 51, 61 first electrode-   12, 22, 32, 42, 52, 62 second electrode-   13A, 23A, 33A, 43A, 53A, 63A first light emitting unit-   13B, 23B, 33B, 43B, 53B, 63B second light emitting unit-   33C, 43C third light emitting unit-   33D, 43D fourth light emitting unit-   43E fifth light emitting unit-   43F sixth light emitting unit-   14A, 24A, 34A, 44A, 54A, 64A first charge generating layer-   14B, 24B, 34B, 44B, 54B, 64B second charge generating layer-   15A, 25A, 35A, 45A first electron transport layer-   16A, 26A, 36A, 46A first light emitting layer-   17A, 27A, 37A, 47A first hole transport layer-   15B, 25B, 35B, 45B second electron transport layer-   16B, 26B, 36B, 46B second light emitting layer-   17B, 27B, 37B, 47B second hole transport layer-   15C, 25C, 35C, 45C third electron transport layer-   16C, 26C, 36C, 46C third light emitting layer-   17C, 27C, 37C, 47C third hole transport layer-   35D, 45D fourth electron transport layer-   36D, 46D fourth light emitting layer-   37D, 47D fourth hole transport layer-   45E fifth electron transport layer-   46E fifth light emitting layer-   47E fifth hole transport layer-   45F sixth electron transport layer-   46F sixth light emitting layer-   47F sixth hole transport layer-   100 lighting device-   111 anode terminal electrode-   113 sealing substrate-   114 sealing member-   115 gap-   200 display device-   300 TFT substrate-   310 base substrate-   320 TFT element-   321 source electrode-   322 drain electrode-   323 gate electrode-   324 gate insulating layer-   330 insulating layer-   400 organic EL element-   410 first partition wall-   420 second partition wall-   500 color filter-   510 first color filter-   520 second color filter-   530 third color filter-   600 sealing substrate

The invention claimed is:
 1. An organic electroluminescent elementhaving a structure in which a plurality of light emitting units eachincluding a light emitting layer made of at least an organic compoundare stacked one on top of another between a first electrode and a secondelectrode with a charge generating layer sandwiched between each pair ofadjacent light emitting units, wherein the organic electroluminescentelement comprises at least two blue light emitting units each includinga light emitting layer formed of a blue light emitting layer which emitsblue light with one or two peak wavelengths in a blue wavelength band,and one of a red/green emitting unit including a light emitting layerformed by stacking a red phosphorescent light emitting layer which emitsred light with one peak wavelength in a red wavelength band and a greenphosphorescent light emitting layer which emits green light with onepeak wavelength in a green wavelength band one on top of the other, anda red-green light emitting unit including a light emitting layer formedof a mixed layer of a red phosphorescent material and a greenphosphorescent material, a light emission intensity of a peak wavelengthin a green wavelength band is lower than a light emission intensity of apeak wavelength in a red wavelength band, white light produced by lightemission of the plurality of light emitting units has an emissionspectrum continuous over a wavelength band of at least 380 nm to 780 nmand has one or two peak wavelengths in a blue wavelength band of 440 nmto 490 nm in the emission spectrum, correlated color temperature of thewhite light is 3300 K or higher, and R6 and R12 among special colorrendering indices (Ri) of the white light are 60 or more and 30 or more,respectively.
 2. The organic electroluminescent element according toclaim 1, wherein characterized in that R12 among the special colorrendering indices (Ri) of the white light is 60 or more.
 3. The organicelectroluminescent element according to claim 1, wherein each blue lightemitting layer is formed of a blue fluorescent light emitting layercontaining a blue fluorescent material.
 4. The organicelectroluminescent element according to claim 3, wherein the blue lightprovided by each of the blue light emitting units including the bluefluorescent light emitting layer includes a delayed fluorescencecomponent.
 5. The organic electroluminescent element according to claim1, wherein the blue light emitting layer is formed of a bluephosphorescent light emitting layer containing a blue phosphorescentmaterial.
 6. The organic electroluminescent element according to claim1, wherein the at least two blue light emitting units comprise two bluelight emitting units which are both identical and which emit blue lightwith the same peak wavelength.
 7. The organic electroluminescent elementaccording to claim 1, wherein the at least two blue light emitting unitscomprise two blue light emitting units which are both different fromeach other and which emit blue light with different peak wavelengthsfrom each other.
 8. The organic electroluminescent element according toclaim 7, wherein the white light has one peak wavelength in a bluewavelength band of 440 nm to 470 nm and one peak wavelength in a bluewavelength band of 470 nm to 490 nm.
 9. The organic electroluminescentelement according to claim 1, wherein the white light produced by thelight emission of the plurality of light emitting units has one peakwavelength in the red wavelength band of 590 nm to 640 nm and one or twopeak wavelengths in the green wavelength band of 500 nm to 560 nm. 10.The organic electroluminescent element according to claim 9, the organicelectroluminescent element capable of providing the white light bycausing the plurality of light emitting units to emit light, wherein theorganic electroluminescent element comprises: a first light emittingunit; a second light emitting unit; and a third light emitting unitformed of one of the at least two blue light emitting units, the firstlight emitting unit and the second light emitting unit are stacked oneon top of the other with a first charge generating layer sandwichedtherebetween, the second light emitting unit and the third lightemitting unit are stacked one on top of the other with a second chargegenerating layer sandwiched therebetween, and the organicelectroluminescent element has a structure in which the secondelectrode, the third light emitting unit, the second charge generatinglayer, the second light emitting unit, the first charge generatinglayer, the first light emitting unit, and the first electrode arestacked one on top of another in this order, when the first lightemitting unit is the at least one red/green light emitting unit or theat least one red-green light emitting unit, the second light emittingunit is one of the at least two blue light emitting units, and when thefirst light emitting unit is one of the at least two blue light emittingunits, the second light emitting unit is the at least one red/greenlight emitting unit or the at least one red-green light emitting unit.11. The organic electroluminescent element according to claim 9, theorganic electroluminescent element capable of providing the white lightby causing the plurality of light emitting units to emit light, whereinthe organic electroluminescent element comprises: a first light emittingunit formed of the red/green light emitting unit or the at least onered-green light emitting unit; a second light emitting unit formed ofthe at least two blue light emitting units; a third light emitting unitformed of the at least one red/green light emitting unit or the at leastone red-green light emitting unit; and a fourth light emitting unitformed of the at least two blue light emitting units, the first lightemitting unit and the second light emitting unit are stacked one on topof the other with a first charge generating layer sandwichedtherebetween, the second light emitting unit and the third lightemitting unit are stacked one on top of the other with a second chargegenerating layer sandwiched therebetween, the third light emitting unitand the fourth light emitting unit are stacked one on top of the otherwith a third charge generating layer sandwiched therebetween, and theorganic electroluminescent element has a structure in which the secondelectrode, the fourth light emitting unit, the third charge generatinglayer, the third light emitting unit, the second charge generatinglayer, the second light emitting unit, the first charge generatinglayer, the first light emitting unit, and the first electrode arestacked one on top of another in this order.
 12. The organicelectroluminescent element according to claim 9, the organicelectroluminescent element capable of providing the white light bycausing the plurality of light emitting units to emit light, wherein theorganic electroluminescent element comprises: a first light emittingunit formed of the at least one red/green light emitting unit or the atleast one red-green light emitting unit; a second light emitting unitformed of the at least two blue light emitting units; a third lightemitting unit formed of the at least one red/green light emitting unitor the at least one red-green light emitting unit; a fourth lightemitting unit formed of the at least one red/green light emitting unitor the at least one red-green light emitting unit; a fifth lightemitting unit formed of the at least two blue light emitting units; anda sixth light emitting unit formed of the at least one red/green lightemitting unit or the at least one red-green light emitting unit, thefirst light emitting unit and the second light emitting unit are stackedone on top of the other with a first charge generating layer sandwichedtherebetween, the second light emitting unit and the third lightemitting unit are stacked one on top of the other with a second chargegenerating layer sandwiched therebetween, the third light emitting unitand the fourth light emitting unit are stacked one on top of the otherwith a third charge generating layer sandwiched therebetween, the fourthlight emitting unit and the fifth light emitting unit are stacked one ontop of the other with a fourth charge generating layer sandwichedtherebetween, the fifth light emitting unit and the sixth light emittingunit are stacked one on top of the other with a fifth charge generatinglayer sandwiched therebetween, and the organic electroluminescentelement has a structure in which the second electrode, the sixth lightemitting unit, the fifth charge generating layer, the fifth lightemitting unit, the fourth charge generating layer, the fourth lightemitting unit, the third charge generating layer, the third lightemitting unit, the second charge generating layer, the second lightemitting unit, the first charge generating layer, the first lightemitting unit, and the first electrode are stacked one on top of anotherin this order.
 13. The organic electroluminescent element according toclaim 1, wherein the white light further comprises a light emissionintensity of the one or two peak wavelengths in the blue wavelength bandof 440 nm to 490 nm such that the light emission intensity of the one ortwo peak wavelength in the blue wavelength band is higher than either ofa light emission intensity of a peak wavelength in a red wavelength bandof 590 nm to 640 nm and a light emission intensity of a peak wavelengthin a green wavelength band of 500 nm to 560 nm in the wavelength band ofthe white light.
 14. The organic electroluminescent element according toclaim 13, wherein the white light has one bottom wavelength in a bluewavelength band and a green wavelength band of 500 nm to 520 nm.
 15. Theorganic electroluminescent element according to claim 14, wherein alight emission intensity of the one bottom wavelength in the bluewavelength band and the green wavelength band of 500 nm to 520 nm islower than a light emission intensity of a bottom wavelength in awavelength band of 570 nm to 590 nm.
 16. The organic electroluminescentelement according to claim 14, wherein a ratio of (B) to (A) ((B)/(A))is 0.50 or smaller, where (A) is a light emission intensity of a peakwavelength having the highest light emission intensity in the wavelengthband of 380 nm to 780 nm and (B) is a light emission intensity of theone bottom wavelength in the blue wavelength band and the greenwavelength band of 500 nm to 520 nm.
 17. The organic electroluminescentelement according to claim 1, wherein characterized in that an averagecolor rendering index (Ra) of the white light is 70 or more.
 18. Theorganic electroluminescent element according to claim 1, wherein thecharge generating layers are formed of electrically insulating layersmade of an electron accepting material and an electron donatingmaterial, and a specific resistance of the electrically insulatinglayers is 1.0×10²Ω·cm or more.
 19. The organic electroluminescentelement according to claim 18, wherein characterized in that thespecific resistance of the electrically insulating layers is 1.0×10²Ω·cmor more.
 20. The organic electroluminescent element according to claim1, wherein each of the charge generating layers is formed of a mixedlayer of different materials and one component of the mixed layer formsa charge transfer complex by redox, and when voltage is applied betweenthe first electrode and the second electrode, charges in the chargetransfer complex move to the first electrode side and the secondelectrode side to cause holes to be injected into one light emittingunit located on the first electrode side of the charge generating layerand cause electrons to be injected into another light emitting unitlocated on the second electrode side of the charge generating layer. 21.The organic electroluminescent element according to claim 1, whereineach of the charge generating layers is formed of a laminate of anelectron accepting material and an electron donating material, and whenvoltage is applied between the first electrode and the second electrode,in an interface between the electron accepting material and the electrondonating material, charges generated by reaction involving electrontransfer between the electron accepting material and the electrondonating material move to the first electrode side and the secondelectrode side to cause holes to be injected into one light emittingunit located on the first electrode side of the charge generating layerand cause electrons to be injected into another light emitting unitlocated on the second electrode side of the charge generating layer. 22.The organic electroluminescent element according to claim 1, wherein thecharge generating layers contain a compound having a structure expressedby formula (1):

where R represents an electron withdrawing group of F, Cl, Br, I, CN, orCF₃.
 23. The organic electroluminescent element according to claim 1,wherein the organic electroluminescent element comprises at least threecolor filters different from one another, and an arrangement of the atleast three color filters different from one another changes the whitelight produced by the light emission of the plurality of light emittingunits to light of a different color.
 24. The organic electroluminescentelement according to claim 23, wherein the arrangement of the at leastthree color filters different from one another is one selected from thegroup consisting of a stripe arrangement, a mosaic arrangement, a deltaarrangement, and a pentile arrangement.
 25. The organicelectroluminescent element according to claim 23, wherein the at leastthree color filters different from one another are a red color filter, agreen color filter, and a blue color filter, and the organicelectroluminescent element has a RGB arrangement in which the threecolor filters different from one another are arranged in turn.
 26. Theorganic electroluminescent element according to claim 25, wherein theorganic electroluminescent element has a RGBW arrangement including theRGB arrangement, and the color filters are not arranged in anarrangement portion of W.
 27. The organic electroluminescent elementaccording to claim 26, wherein the RGBW arrangement is one selected fromthe group consisting of a stripe arrangement, a mosaic arrangement, adelta arrangement, and a pentile arrangement.
 28. A display device,comprising: the organic electroluminescent element according to claim23.
 29. The display device according to claim 28, wherein the displaydevice comprises a base substrate and a sealing substrate which areformed of flexible substrates, and the display device is flexible.
 30. Alighting device, comprising: the organic electroluminescent elementaccording to claim
 1. 31. The lighting device according to claim 30,wherein the lighting device comprises an optical film on a lightextraction surface side of the organic electroluminescent element. 32.The lighting device according to claim 30, wherein an average colorrendering index (Ra) of the white light is 80 or more.
 33. The lightingdevice according to claim 30, wherein the lighting device comprises abase substrate and a sealing substrate which are formed of flexiblesubstrates, and the lighting device is flexible.